Fantastic, I was trying to force users to only insert urls from my domain and this worked a treat!
Cheers mate...
var
FirstDig
FirstDig
= Left($.rawValue, 20) if
(FirstDig <> "http://mydomain.co.uk") then
xfa.host.messageBox("Please use http://mydomain.co.uk, files are more secure there!")
$.rawValue
= null
endif