Not sure what you are trying to ask. It sounds like you are trying to make a custom link. If so,
What do you have for Prepend and Append URL text?
Is it enabled in Admin settings for the plugin?
Is it enabled in the User's profile?
What did the user put in for that field in their profile?
Just trying to understand what exactly you want. I'm not familyar with wepay.com. Can you give me an example of the link you would like to end up with and which part of the link you want the user to provide?
Nick