pues me decidi a buscar la solucion.y tras muchas horas de trabajo he encontrado un sustituto del index. es la propiedad de evento TabIndex.
aqui esta el codigo:
Public Class Form1
Dim btn As Button
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
btn = CType(sender, Button)
Call button()
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
btn = CType(sender, Button)
Call button()
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
btn = CType(sender, Button)
Call button()
End Sub
Private Sub button()
If btn.TabIndex = 1 Then MsgBox("1")
If btn.TabIndex = 2 Then MsgBox("2")
If btn.TabIndex = 3 Then MsgBox("3")
End Sub
End Class