Cannot use parentheses when calling a Sub

Jeg får fejlen:
Cannot use parentheses when calling a Sub

/hg/test.asp, line 6

ErrorMsg("200","test")
----------------------^

Linie 6 og ned:

Function ErrorMsg(ErrorNo,ErrorMs)
Response.clear
Response.expires = 0
Response.write "<!DOCTYPE HTML PUBLIC ""-//W3C//DTD HTML 4.01 Transitional//EN"">" & vbCrLf
Response.write "<head><title>Fejl</title></head><body><b>Fejl:</b><br>" & vbCrLf
Response.write "<b>" & ErrorNo & "</b> - " & ErrorMs & "<br>Hvis denne fejl fortsætter...<br>" & vbCrLf
Response.end
End function

Hvad er der galt?