asp Function that verify that the username contains very characters

<%

'*********************************

'Function: IsValidUserName(byValUserName)

'Parameter: UserName, username

'Author: Alixi

'Date: 2007/7/15

'Description: Verify whether the user name contains illegal characters, without illegal characters Return: true

'Example: IsValidUserName(byValUserName)

'*********************************

FunctionIsValidUserName(byValUserName)

Dimi,c

IsValidUserName=True

Fori=1ToLen(UserName)

c=Lcase(Mid(UserName,i,1))

IfInStr("$!<>?#^%@~`&*();:+='""",c)>0Then

IsValidUserName=False

ExitFunction

EndIF

Next

EndFunction

%>