Simple programming help with the Prime

[Angus]

I was trying to use the Stack.
Your code works nicely when calling tohex() as written, thank you! I will forget my way in the future.
I try to call tohex() from within an other program I have problems. I want to launch a menufor conversion but suppose I just wanted to have a user key on shift+minus for hex conversion.

KEY KS_Minus()
BEGIN
LOCAL reval;
retval:=tohex(1); //this gives an error when called without number of pops retval();
RETURN retval;
END;

However if I hit shift+minus the function app is started... Any ideas what I am doing wrong?