I've seen spray paint made specially for black trim around windows. To use it, you'd probabally need to sand the old paint off (at least where it's comming off now), mask off EVERYTHING around it, and spray on a few light coats. If you're inexperienced with spray paint, get lots and lots of advice before you do this.
BTW- if you're starting to rust now, get some rust treatment NOW! It will get worse and worse and worse if you don't , and be especially worried when its near your windows (which makes body work VERY expensive since you might need a specialist to remove the windows and reweld stuff...). The rust treatment will melt/convert the rust into black sandable primer and temporarily inhibit the spread of the rust. Professional body work typically can run into the thousands, so attack it now before it gets that bad. The rust treatment ("ONE STEP" by Mar Hyde or Bondo) is available at any atuo parts store.
Sorry for the long post, but I would hate to see someone else go through what I'm going through (with rusting).