Forcing User to Fill Out Second Form

I have two different forms that are on ASP pages that users must fill out. Is there a way for me to force the user to fill out the second form on the next ASP Page if he/she has filled out the first form? If the user starts to leave the page, I would like for a message box to show up saying, "You must fill out this form". I think that there may be a Javascript code for this somewhere.