Are DIY A/C leak detector kits worth it?

['97ventureowner]

I just had my '95 Buick Roadmaster's a/c recharged about a month ago. Everything was fine for about 2 weeks and then the a/c started blowing warm air, which leads me to believe there is a leak somewhere in the system. I see at the parts stores they sell a can of R 134a with a dye in it. You are supposed to install it in your a/c system, and then run it for at least 20 minutes to circulate the refrigerant with the dye through your system. You then take a UV light and go over the system looking at all the components including the hoses, connections etc. for any signs of the dye. The can of R134a with the dye runs $9.95/can. Has anybody used something like this with good results, or is it not worth it? I also noticed they sell another product which is a can of R134a with a sealant in it that is supposed to circulate through your a/c system and seal small leaks at your connections, gaskets, and any areas where the leak is small enough to seal. There also is a red dye contained in the can which is supposed to come out of any leak that is too large for the sealer to be able to seal properly, letting the vehicle owner or mechanic know where the larger leak is that needs to be repaired another way. Again, has anybody had any experience with a product like this and care to comment on it's effectiveness? Thank you.