The simplest approach is to update the link when you have sufficient data to make a decision.
But more information on the link itself would be required to comment further in that direction.
The next simplest approach is to have a single form, but which has 3 different "behaviors" - ie merging all 3 forms into 1. This is possible in some cases, less easy to do in others.
Finally, you can't use a NetWebSource as the "decider". But you can use a NetWebPage. that though would have ancillary issues if you were attempting to go to a popup form.
cheers
Bruce