Render and Check the Returned Path

Pass the output alpha field with Share Y so the routine can return the full PNG pathname. A blank starting value requests a name in the configured chart directory; a full pathname selects an explicit destination. For the first test, use a new filename and a destination you have already tested as writable.

      PASS         <chart_pathname>           FIELD            SHARE? Y
      SUBR     0CD .CHART RENDER                    SUBPROCESS   END? N  FAIL 0
      IF       0CD .CHART RENDER              NE

This is the documented call pattern. Replace <chart_pathname> with your alpha work field. Put your application's error branch under the nonblank-result test and include .CHART RENDER ERROR in its diagnostic. Keep the call in a separate subprocess as shown by the vendor.