If the control has no scroll bars the OffsetChanged and OversizeChanged events are not fired. Use the ScrollBars property of the control to determine which scroll bars are visible within the control. 

The following VB sample displays the new scroll position when user scrolls horizontally the control:

Private Sub Gantt1_OffsetChanged(ByVal Horizontal As Boolean, ByVal NewVal As Long)
    If (Horizontal) Then
        Debug.Print "The horizontal scroll bar has been moved to " & NewVal
    End If
End Sub

The following VC sample displays the new scroll position when the user scrolls vertically the control:

void OnOffsetChangedGantt1(BOOL Horizontal, long NewVal) 
{
	if ( !Horizontal )
	{
		CString strFormat;
		strFormat.Format( "NewPos = %i\n", NewVal );
		OutputDebugString( strFormat );
	}
}

The following VB.NET sample displays the new scroll position when the user scrolls vertically the control:

Private Sub AxGantt1_OffsetChanged(ByVal sender As Object, ByVal e As AxEXGANTTLib._IGanttEvents_OffsetChangedEvent) Handles AxGantt1.OffsetChanged
    If (Not e.horizontal) Then
        Debug.WriteLine(e.newVal)
    End If
End Sub

The following C# sample displays the new scroll position when the user scrolls vertically the control:

private void axGantt1_OffsetChanged(object sender, AxEXGANTTLib._IGanttEvents_OffsetChangedEvent e)
{
	if ( !e.horizontal )
		System.Diagnostics.Debug.WriteLine(e.newVal);
}

The following VFP sample displays the new scroll position when the user scrolls vertically the control:

*** ActiveX Control Event ***
LPARAMETERS horizontal, newval

if ( 0 # horizontal )
	wait window nowait str( newval )
endif