Problem with DCAM camera - 'ShutterControl'

Hello all, I'm using a Firewire camera to acquire pictures in my setup. In my code I'm using commands as the following to control the shutter:

set(TXD14.source,'ShutterControl','relative');

When I run the code I get an error saying that 'ShutterControl' is not a valid command for my instance. Could anyone please suggest me an alternative? Or indicate me a way to show all the possible available commands?

Thanks in advance. Enrico