It's HOT and the A/C's out!!

I have a 1994 Honda Accord LX that seems to have a freon leak. At about this time last year the A/C started making a funny noise and pretty soon it was blowing hot air alternating with cold air for 30 second intervals. We had the A/C checked out. The mechanic said it was low on freon so he refilled it. He said there might be a leak and to watch it. It worked great all winter and the first half of this summer.

Well, last week it died again, only this time it went out a lot quicker. I'm sure there's a leak somewhere in it.

What is the best action at this point? The car is old and has nearly

200,000 miles. I don't want to spend hundreds on it, but it is very hot now in Utah which makes having no A/C very uncomfortable. I've seen refill kits in the newspaper adds that claim to have leak stopping abilities. Do those work?

I would appreciate any suggestions or words of wisdom.

Thanks