Well, as you know, I'm a scheme fan and I think that GNU have definitely done The Right Thing in making a scheme their main extension language, although it's not perfect and is woefully under-used at the moment, even by official GNU software. Hopefully it can become as common as VB is on that other platform, as there's scope to do so much more with it. What we really need are more good libraries for guile and more good simple introductions to it. Teach Yourself Scheme in Fixnum Days is pretty good, though.
So for the solution to the problem you have *now*, ie building cross-platform simple GUI non-C apps, I'd suggest taking a look at Visual Tcl, which should easily cope with having a few functions added. Sadly, the docs are rather thin on the ground, but it is basically Tcl behind the scenes, which is a fairly simple language.
I think Java would be overkill for such a small app, but that's probably an equally good route, and I don't know Kylix well enough to comment.
But I don't really understand why you think scripting means that you can't have functions. The distinction between a scripting language and a programming language is somewhat arbitrary these days.