Any property (including arrays) cannot be passed by reference.
You have to copy it to a local array, pass local array by reference and then copy back if necessary.

LOCAL ARRAY laParam[1]
ACOPY(thisform.ayParam, laParam)
llSuccess = PXREQUERY(ALIAS(), .T., @laParam)

>
>I am trying to pass a form's array property by reference.
>myform.ayparam, which is a two dimensional array
>
>the call:
>llSuccess = PXREQUERY(ALIAS(), .T., @thisform.ayParam)
>
>the function:
>function pxrequery( tuView, tlForce, taViewParams)
>exteranl array taViewParams
>
>
>on the call line, the error is 13, alias not found
>
>can I do this? and if so, what am i doing wrong
>