Message Box In Reporting Services

I have used this code pasted below to show message box in reports in Reporting services 2000.It works and pops up but only in development environment but not in production.I mean to say it works in Preview mode but when I have deployed the report it doesn't work.Doesn't even show any error message.

I don't know what would be the code and which assembly file should i Include. Any Ideas ......




Public Function FixDigits(ByVal s As string)
dim msg1 as string
msg1="Parameter is not a 20 digit number"
dim msg2 as string
msg2= "Parameter is not a number"

Dim title As String
title="Attention"
Dim style As MsgBoxStyle
Dim response As MsgBoxResult

style = MsgBoxStyle.OKONLY
if len(s)<>20 then
response = MsgBox(msg1, style, title)


elseif IsNumeric(s)=false then
response = MsgBox(msg2, style, title)

else
end if

End Function