live templates with optional arguments

1) How can I create a live template which may have optional arguments?

function(param1, param2, param3) {
     $END$
}

Where param2 and param3 are optional. I'd like to either TAB thru one (or both) of them or DEL if I don't want the parameter. Result would be

function(param1) { ... }

OR

function(param1, param2) { ..}

OR

function(param1, param3) {...}