You would have been better off using a Sealing application enabled robot instead of Arc Welding as these have specific flow orientated commands available for gun control and distance on/off.
In this case then, I suggest you program using standard AS Language Manual then, you should be able to achieve your requirement that way.
Look at CP, ACCURACY and MOTION TYPE references including LMOVE/JMOVE/C1MOVE/C2MOVE Motion instructions.