[WD22] Radio button inside Looper

Good morning, I'm trying to modify the captions of a radio button that is inside a looper by programming, I use the next code:

LOOP_Cuestionario[nFila].RADIO_OpcionesMultiples[stOpc.nOPC_ORDEN]..Caption = stOpc.sOPC_TEXTO

But when I run it, windev says that the operator [] is not supported by the radio control. Any ideas as how to solve this?