PhysicsCollide on a vehicle?

Could you do PhysicsCollide on a vehicle? like this.

[LUA]function beltcrash( entity, think, ply )
local ent = self.Entity
ent:AddCallback( “PhysicsCollide” )
if ent:getclass() == prop_vehicle_jeep then
if ( data.Speed > 50 ) then ent:EmitSound( Sound( “npc/roller/mine/rmine_shockvehicle2.wav” ) )
print (ent:GetDriver())
print (ent:GetPassenger())
print (ent:VC_GetPlayers())
ent:AddCallback( “PhysicsCollide”, beltcrash [/LUA]

If this doesn’t work. WHat way would be good to fix a function for this?

Can you do minuse on a current value? like this:

self.todone = table.GetFirstValue(todone) -1

This worked.
function ENT:Think(CurTimeDelay)
if self.hasstarteditem then

if CurTime() < nextrun then return end
nextrun = CurTime() + 5
self.todone = self.todone - 1
print (self.todone)