Sub AAA()
Dim StartCol As Long
Dim EndCol As Long
Dim ColNdx As Long
Set sht = Sheets(x)
StartCol = 1 ' column A
EndCol = 28 ' column AB
For ColNdx = EndCol To StartCol Step -1
If Application.CountA(sht.Columns(ColNdx)) = 1 Then
sht.Columns(ColNdx).Delete
End If
Next ColNdx
End Sub

Once worked fine, but now error on this line....

Set sht = Sheets(x)