[late reply coming in]
Hi, just saw the topic now and don't know if you already solved it. The way I do it is to use Gimp (a freeware program) to create a simple texture (for glass I'd go with 64x64 or something like that) and use the toolbar to add the alpha channel. Then I use the Eraser tool to make it half-transparent - the last thing to do is to save it as filename.tga and convert it to .pac or .paa with texView (also available on OFPEC). I hope that helps.