Looks like you need following parameters to exec this script:
[player,0] exec "switch.sqs"
:note - the GroupArray value, for which i wrote 0 here
can be 0,1,2,3, because there are 4 squads.
In this case, you would take controll over group1
(GroupArray select 0 = group1 from the array: GroupArray)
:edit - ah yes, and to be able to switch between all the four
squads, you need to setup 4 triggers (one for each group)
~S~ CD