Trudy,
Unfortunately now you are getting into a possibly dangerous area and I would recommend taking the vehicle to a shop. R134a is a refridgerant and as such discharging it yourself could cause some nasty freeze burns. Not to mention there is possibly a tracer dye in the stuff you used already, designed to help detect leaks.
You may get lucky though and a shop, or maybe a good auto parts store will do it for little or no cost since they may be able to recover some of it for use on their own or in other cars.
Hope this helps
Regards,
Frank