If you have not done so, please read about "Communication" first, within cards I will continue the thread startet there.
There are a couple of important things to know about cards and scripting (following applies for non immediate scripts):
the scripts are called via "events"
if a script needs feedback from a player it by itself issues an "event"
these calls are asynchron, which means you don't get feedback directly instead, exactly the same script is called a second time, and the script itself must figure out, if an answer is available
the card must MUST M U S T! set the variable "bRet"
if bRet is set to false, the execution of the script is taken to be not successful, which means, it will be called again!
if bRet is set to true, the script is ended successfully and will not be called again
Note: even if something you might feel was not successfull, has happened if the card is "finished" and the script should not be called again you MUST set bRet = true; (per default bRet is set to true, but you SHOULD allways set it what you want it to be anyway)