local group g=CreateGroup()
local unit ig
     call GroupEnumUnitsInRange(g,X,Y,radius,filter)
loop
     set ig=FirstOfGroup(g)
     ...
     call GroupRemoveUnit(ig)
     exitwhen ig==null
endloop
call DestroyGroup(g)
set g=null
set ig=null

globals
 group gr_temp=CreateGroup()
 boolexpr bx=null
endglobals

function ActionWithPickedUnit takes nothing returns boolean
 //
 return false
endfunction

function init takes nothing returns nothing
 set bx=Condition(function ActionWithPickedUnit)
endfunction

// --->
 call GroupEnumUnitsInRange(gr_temp , x, y, r, bx)
// <---