yeah like this...
tank1 = "T80" createvehicle getpos g1
"SoldierECrew" createunit [getpos g1, east1, "c1 = this", 1, "SERGEANT"]
"SoldierECrew" createunit [getpos g1, east1, "c2 = this", 1, "CORPORAL"]
"SoldierECrew" createunit [getpos g1, east1, "c3 = this", 1, "PRIVATE"]
c1 moveincommander tank1
c2 moveingunner tank1
c3 moveindriver tank1
g1 = a gamelogic or a marker, if marker it is getMarkerPos "g1"
east1 = the group the units are assigned to
c1,c2,c3 = the names of the vehicle crew
To spawn units in to a group you have to place a single unit on your map and place this in his initfield : east1=group this; deleteVehicle this.