I use this code in combination with a registry-key (user-part)

*************
' Show About screen
If GetSetting(appname:="YourExcelSheetName", Section:="About", _
Key:="Aboutscreen") = "" Then GoTo Next2do1
If GetSetting(appname:="YourExcelSheetName", Section:="About", _
Key:="Aboutscreen") = True Then GoTo Next2do2

Next2do1:
UserForm1.Show

Next2do2:
********
Hope this helps
Rob