Use the ItemFromPoint property to get the item from the point specified by the {X,Y}. The X and Y coordinates are expressed in client coordinates, so a conversion must be done in case your coordinates are relative to the screen or to other window. 

The ItemFromPoint property returns:

• the handle of the item from the current cursor position, if the X and Y parameters are -1. The ItemFromPoint property returns 0, if not item is found.
• the number of rows from current cursor position to the last visible item, if the X is 0 and Y parameter is -1. The ItemFromPoint property returns 0, if the cursor hovers any item, else it returns a positive value, that indicate the number of items between the last visible item and the current cursor position. For instance, you can use this option, to add items to the cursor, once the user clicks the empty area of the items section of the control. 

Use the ColumnFromPoint property to retrieve the column from cursor. Use the DateFromPoint property to specify the date from the cursor. Use the SelectableItem property to specify the user can select an item. Use the BarFromPoint property to get the bar from the point. Use the LinkFromPoint property to get the link from the point. 

The following VB sample prints the cell's caption from the cursor ( if the control contains no inner cells. Use the SplitCell property to insert inner cells ) :

Private Sub G2antt1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
    On Error Resume Next
    ' Converts the container coordinates to client coordinates
    X = X / Screen.TwipsPerPixelX
    Y = Y / Screen.TwipsPerPixelY
    Dim h As HITEM
    Dim c As Long
    Dim hit As EXG2ANTTLibCtl.HitTestInfoEnum
    ' Gets the item from (X,Y)
    h = G2antt1.ItemFromPoint(X, Y, c, hit)
    If Not (h = 0) Then
        Debug.Print G2antt1.Items.CellValue(h, c) & " HT = " & hit
    End If
End Sub

The following VB sample displays the cell's caption from the cursor ( if the control contains inner cells ):

Private Sub G2antt1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
    On Error Resume Next
    ' Converts the container coordinates to client coordinates
    X = X / Screen.TwipsPerPixelX
    Y = Y / Screen.TwipsPerPixelY
    Dim h As HITEM
    Dim c As Long
    Dim hit As EXG2ANTTLibCtl.HitTestInfoEnum
    ' Gets the item from (X,Y)
    h = G2antt1.ItemFromPoint(X, Y, c, hit)
    If Not (h = 0) Or Not (c = 0) Then
        Debug.Print G2antt1.Items.CellValue(h, c) & " HT = " & hit
    End If
End Sub

The following VB sample displays the index of icon being clicked:

Private Sub G2antt1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
    Dim i As HITEM, h As HitTestInfoEnum, c As Long
    With G2antt1
        i = .ItemFromPoint(X / Screen.TwipsPerPixelX, Y / Screen.TwipsPerPixelY, c, h)
    End With
    If (i <> 0) or ( c <> 0 ) Then
        If exHTCellIcon = (h And exHTCellIcon) Then
            Debug.Print "The index of icon being clicked is: " & (h And &HFFFF0000) / 65536
        End If
    End If
End Sub

The following C# sample displays the caption of the cell being double clicked ( including the inner cells ): 

	EXG2ANTTLib.HitTestInfoEnum hit;
	int c = 0, h = axG2antt1.get_ItemFromPoint( e.x, e.y, out c, out hit );
	if ( ( h != 0 ) || ( c != 0 ) )
		MessageBox.Show( axG2antt1.Items.get_CellValue( h, c ).ToString() );

The following VC sample displays the caption of the cell being clicked:

#include "Items.h"

static CString V2S( VARIANT* pv, LPCTSTR szDefault = _T("") )
{
	if ( pv )
	{
		if ( pv->vt == VT_ERROR )
			return szDefault;

		COleVariant vt;
		vt.ChangeType( VT_BSTR, pv );
		return V_BSTR( &vt );
	}
	return szDefault;
}

void OnMouseDownG2antt1(short Button, short Shift, long X, long Y) 
{
	long c = 0, hit = 0, hItem = m_g2antt.GetItemFromPoint( X, Y, &c, &hit );
	if ( ( hItem != 0 ) || ( c != 0 ) )
	{
		CItems items = m_g2antt.GetItems();
		COleVariant vtItem( hItem ), vtColumn( c );
		CString strCaption = V2S( &items.GetCellValue( vtItem, vtColumn ) ), strOutput;
		strOutput.Format( "Cell: '%s', Hit = %08X\n", strCaption, hit );
		OutputDebugString( strOutput );
	}
}

The following VB.NET sample displays the caption from the cell being clicked:

Private Sub AxG2antt1_MouseDownEvent(ByVal sender As Object, ByVal e As AxEXG2ANTTLib._IG2anttEvents_MouseDownEvent) Handles AxG2antt1.MouseDownEvent
    With AxG2antt1
        Dim i As Integer, c As Integer, hit As EXG2ANTTLib.HitTestInfoEnum
        i = .get_ItemFromPoint(e.x, e.y, c, hit)
        If (Not (i = 0) Or Not (c = 0)) Then
            Debug.WriteLine("Cell: " & .Items.CellValue(i, c) & " Hit: " & hit.ToString())
        End If
    End With
End Sub

The following C# sample displays the caption from the cell being clicked:

private void axG2antt1_MouseDownEvent(object sender, AxEXG2ANTTLib._IG2anttEvents_MouseDownEvent e)
{
	int c = 0;
	EXG2ANTTLib.HitTestInfoEnum hit;
	int i = axG2antt1.get_ItemFromPoint( e.x, e.y, out c,out hit );
	if ( ( i != 0 ) || ( c != 0 ) )
	{
		string s = axG2antt1.Items.get_CellValue( i,c ).ToString();
		s = "Cell: " + s + ", Hit: " + hit.ToString();
		System.Diagnostics.Debug.WriteLine( s );
	}
}

The following VFP sample displays the caption from the cell being clicked ( the code should be in the G2antt1.MouseDown event ):

*** ActiveX Control Event ***
LPARAMETERS button, shift, x, y

local c, hit
c = 0
hit = 0
with thisform.G2antt1
	.Items.DefaultItem = .ItemFromPoint( x, y, @c, @hit )
	if ( .Items.DefaultItem <> 0 ) or ( c <> 0 )
		wait window nowait .Items.CellValue( 0, c ) + " " + Str( hit )
	endif
endwith