Mr Rhodes,
[vba]Sub ShowWhoLockedIt()
Dim i As Long, j As Long, tStr As String
With ThisWorkbook.VBProject.VBComponents("ThisWorkbook").CodeModule
tStr = .Lines(1, .CountOfLines)
End With
i = InStr(1, tStr, "application.username = """, vbTextCompare) + 24
j = InStr(i, tStr, """", vbTextCompare)
MsgBox Mid(tStr, i, j - i)
End Sub[/vba]Matt

EDIT: You may want to consider using something other than 'Application.UserName', as that can be set by the user and they could change theirs to match yours and get into the file. See http://vbaexpress.com/kb/getarticle.php?kb_id=768 for your options