Modifying an external array within a loop

Please attach your worksheet (upper left - "Use advanced editor")

What does "not work".

Did you expect the nested for-loops to have any effect on the worksheet variable g31? Is hasn't.

Inside program structures everything on the left of a local assignment is treated as a local variable, so the variable g31 you change in your program has nothing to do with the WS variable you obviously wish to change.

Solution: Assign the program a variable by writing "ge31:=for j ....". Then as the first line of your program write "g31<-- g31". While this may look silly, keep in mind, that the left g31 is the uninitialized local variable, whereupon the right g31 is the worksheet variable. As from now on a local g31 exists, MC would use this local variable on the RHS of the subsequent local assigments, too.

At the end of your programm add "return g31"

This should do the job

In short: You cannot change a worksheet variable from within a program. Only way to do is to assign the program result to that variable.