As I understand your code, this line:
strRole = DLookup("access_level", "user", "[UserID]'" & Me.cboUser.Value & "'")
needs to be changed to:
strRole = DLookup("access_level", "user", "[UserID]='" & Me.cboUser.Value & "'")
to set a value for strRole but once that is done I can't see where or how you are using strRole.