How to save script routine result in variable?

Hi,

I have keyword test (KWT) which has some variables. I call a script routine (from KWT) which generates string from variables.

I need to use generated string as filename in KWT. 

I have two questions:

How can I get string value from the script routine?

Script routine is not able to retrieve two variables from KWT for which I have used set variable value.

Thanks,

Samixa