Our realtor organization would like to have a link from their website to our bank's website. they propose that if realtors click on our ad, then it would direct the realtor to our bank's website.

I have to add that the organization is doing this with our "permission" that is to say that we know the link is going to happen. As opposed to they linking to our bank without us knowing.

I think they need to have a "speed bump" saying that the realtor is leaving the realtor website and the realtor cannot go "back" to the realtor org webpage.

The realtor org said that they cannot put in customized java scrips, so they cannot accommodate our request. Is this necessary? Can we instead have on our "ad" the webaddress?

Speed bumps are not a "requirement" but a good idea. They should be more interested in it than you. That said, if you'd be more comfortable and they agree, seek an alternative to java script.

Put your link in an area that says "these links take you to a web site not controlled by us..."

Color code the link or a border around the link or add an icon next to it and a footnote (not hidden in fine print) that says "these links take you to ..."