Can you tell me what is wrong with "IsNothing" in my code?

Private Sub Email_AfterUpdate()
' If you just type in an email name: Somebody@hotmail.com
' Access changes it to: Somebody@hotmail.com#http://somebody@hotmail.com# !!
' This code tries to fix it
Dim intI As Integer
   ' Don't do anything if email is empty
   If IsNothing(Me.PMemailAddress) Then Exit Sub
   ' Fix up http:// if it's there
   Me.PMemailAddress = Replace(Me.PMemailAddress, "http://", "mailto:")
   ' Now look for the first"#" that delimits the hyperlink display name
   intI = InStr(Me.PMemailAddress, "#")
   ' And put the person name there instead if found
   If intI > 0 Then
     Me.PMemailAddress = (Me.PMemailAddress + " ") & Me.LastName & _
       Mid(Me.PMemailAddress, intI)
   End If
End Sub