Sorry. I forgot to disable EnableEvents. Should be:

Private Sub Worksheet_Change(ByVal Target As Range)
With Target
If .Count 1 Or .Column < 2 Then Exit Sub
If LCase(Trim(.Value)) = "y" Or _
LCase(Trim(.Value)) = "yes" Then
Application.EnableEvents = False
.Value = "Yes"
Application.EnableEvents = True
End If
End With
End Sub
"Greg Wilson" wrote:

Assumed is that you want this behavior to occur in column B. Paste to the
worksheet's class module: Right click the worksheet tab Select View Code
Paste to the code module.

Private Sub Worksheet_Change(ByVal Target As Range)
With Target
If .Count 1 Or .Column < 2 Then Exit Sub
If LCase(Trim(.Value)) = "y" Or _
LCase(Trim(.Value)) = "yes" Then
.Value = "Yes"
End If
End With
End Sub

Regards,
Greg