CALL PROCESS calls the Outside call phase of the layout displayed in the frontmost window of process processID. If process has no window or no layout is currently displayed, nothing happens.
If you pass -1 in process instead of a process reference number (processID), all the windows of any process that contains interprocess variables will be redrawn. In order not to slow down procedure execution, 4th DIMENSION does not redraw interprocess variables each time they are modified.