bueno la verdad esto es algo facil de hacer...
 
el asunto va  así.. 
Código:
 Private Sub Form_Load()
MSHFlexGrid1.Cols = 5
MSHFlexGrid1.Rows = 30
End Sub
Private Sub MSHFlexGrid1_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single)
If Button = 2 Then
MSHFlexGrid1.Row = MSHFlexGrid1.MouseRow
MSHFlexGrid1.Col = MSHFlexGrid1.MouseCol
 MsgBox "Fila: " & MSHFlexGrid1.Row & " Columna: " & MSHFlexGrid1.Col
End If
End Sub
  nos vemos..