Unfortunatly it still wants an Object!
I made a little test-script:
_i = 0
_flag = format["%1%2","flag",_i]
"_x setFlagTexture ""usa_vlajka.pac""" forEach [_flag]
But then I get the error message:
'_x setFlagTexture "usa_vlajka.pac"|#|': Error setFlagTexture: Type String, expected Object