Locking user functions

We often see in the BBS to prohibit users to post, or lock users can not login, and so on, let's take a look at how these features are implemented by the program.
Sub LockUser ()
Dim UserStatus
If XmlDoc.documentElement.selectSingleNode ("UserStatus") is nothing Then
Messenge = "<li> parameter illegal, abort request. </li> "
Status = 1
Exit Sub
ElseIf not IsNumeric (XmlDoc.documentElement.selectSingleNode ("UserStatus"). Text) Then
Messenge = "<li> parameter illegal, abort request. </li> "
Status = 1
Exit Sub
Else
UserStatus = CLNG (XmlDoc.documentElement.selectSingleNode ("UserStatus"). Text)
End If
If userstatus = 0 Then
Newasp.execute ("UPDATE nc_user SET userlock=0 WHERE username= '" & Username & "")
Else
Newasp.execute ("UPDATE nc_user SET userlock=1 WHERE username= '" & Username & "")
End If
Status = 0
End Sub