So... here's what I want to do...
I would like... part of my iframe's scroll bar transparent.... and another part to be opaque... Is this possible? What would the CSS for it be?

I've done a bit more playing around, and I've got down to this:

filter:alpha(color=ffffff opacity=100) chroma(color=377FC7 opacity=50);
except... it doesn't work!

So my newest question would be... is it possible to use more than one filter?

Try something more like this:
filter:alpha(opacity=50) chroma(color=#377FC7);

Why thank you! That works beautifully!