How to get the approached unit?

Return bug functions in your custom script code area:

// this gives the integer value of any handle (unit, trigger, item, destructible, etc.)
function H2I takes handle value returns integer
	return value
	return 0
endfunction

// this simply converts that integer into a string ... so you don't have to go I2S(H2I( handle )) all the time
function H2S takes handle value returns string 
	return I2S(H2I(value))
endfunction

// this takes a stored integer value for a unit and returns the unit
function I2U takes integer value returns unit 
	return value
	return null
endfunction

// needed variables which you need to use (i used your naming scheme)
temp_string
temp_integer
temp_trigger
IQ_unit


// this gives you an idea of how to setup what you need
setup
    Events
        Map initialization
    Conditions
    Actions
        Game Cache - Create a game cache from YourMap // at map init you need to create a game cache, unless you already use one
        Unit Group - Add SomeUnits <gen> to MyUnits // put your units in your group
        Unit Group - Pick every unit in MyUnits and do (Actions)
            Loop - Actions
                Custom script:   set udg_temp_trigger = CreateTrigger() // dynamically create a trigger
                Trigger - Add to temp_trigger the event (Unit - A unit comes within 132.00 of (Picked unit)) // add the event to the trigger
                Custom script:   call TriggerAddAction( udg_temp_trigger, function Trig_fires_Actions ) // add the action to the trigger ... note that if you use a gui trigger, the actions for it are always function Trig_insert_your_trigger_name_here_Actions where _ represents a space
                Custom script:   set udg_temp_string = H2S( udg_temp_trigger ) // store the integer value of the trigger as a string
                Custom script:   set udg_temp_integer = H2I( GetEnumUnit() ) // get the integer value of the unit the trigger fires for
                Game Cache - Store temp_integer as approached of temp_string in (Last created game cache) // store the unit in the gamecache using the trigger as a key ... gamecache stores things like this: cache > folder > key > value, in this case the cache refers to the last created one, the folder is the string for the trigger, and the key is the string approached

// the actions for your trigger when the event fires
fires
    Events
    Conditions
    Actions
        Custom script:   set udg_temp_string = H2S( GetTriggeringTrigger() ) // triggeringtrigger is the trigger that is fired, store it as a string
        Set temp_integer = (Load approached of temp_string from (Last created game cache)) // get the stored integer value of the unit you created the trigger for
        Custom script:   set udg_IQ_unit = I2U( udg_temp_integer ) // get the unit that integer value represents
        Game - Display to (All players) the text: (String((Unit-type of (Triggering unit)))) // shows you the name of the approaching unit
        Game - Display to (All players) the text: (String((Unit-type of IQ_unit))) // shows you the name of the approached unit

set udg_temp_trigger = CreateTrigger() 
call TriggerAddAction( udg_temp_trigger, function Trig_fires_Actions )

For each (Integer A) from 1 to array_count, do (Actions)
    Loop - Actions
        If (All Conditions are True) then do (Then Actions) else do (Else Actions)
            If - Conditions
                trigger_array[Integer A] Equal to (This trigger)
            Then - Actions
                Set IQ_unit = unit_array[Integer A]
                Custom script:   exitwhen true /// maybe 3 lines of custom script :-\
            Else - Actions

unit comes wihtin range of unithere

set theunituneedtopick = random unit wihtin samedistance of triggering unit matching - unit - matching unit not = triggering unit