Workbook_BeforeSave / Cells with required entry / Catch-22

You need a very small change to your current code:-

Private Sub Workbook_BeforeClose(Cancel As Boolean)
If Sheets("yourSheet").[a1] = "" Then
Cancel = True
MsgBox "Can't save No entry for A1"
Else
Cancel = False
End If
End Sub

Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
If Sheets("yourSheet").[a1] = "" Then
Cancel = True
MsgBox "Can't save No entry for A1"
Else
Cancel = False
End If
End Sub

HTH,
Dax.

There's probably an easier way, but a workaround, would be to write an AutoOpen event to check cell A1 and clear contents if it is a "specific value". Then add your other code and enter the "specific value" in A1 and save. Just make sure your "Specific value" is a value which will not occur in use.