exit when x > 3, not x < 3, cause x goes x = x + 1.
The custom script call DestroyForce[x] is false. It should be for example: call DestroyForce (udg_Blabla[x])
What type is your variable? It should be "Integer", not "Real". By the way, use one "_" in the call DestroyGroup (udg_Neji...), you used two by mistake: (udg__Neji...).