Activate worksheet

[jwongsf]

I do not know if I have this written correctly, I would like to have the sub - Retro run whenever some one opens this worksheet - "FORM". The retro is also suppose to test cell H12 to see if it is blank before running the msgbox, Can any one help me with this,,,

Private Sub workbook_sheetactivate(ByVal SH As Object)
If TypeName(SH) = "Worksheet" Then Retro
Range(a1).Select

End Sub

Private Sub Retro()
' if statement to check H12 to see if blank, if blank then preceed if not then exit.


ans = MsgBox("Is this Funding Change Retro?", vbYesNo)
    Select Case ans
        Case vbYes
             Sheets("Funding Source Change Form").Select
             Range("F5").Select
            ActiveCell.FormulaR1C1 = "X"
            Range("H12").Select
            Exit Sub
        Case vbNo
             Range("h12").Select
        Exit Sub
     End Select
End Sub