For Loop Code issue

Look carefully at the error message that Prime gives: "This value must be an integer"

Pw is a vector. You are using j to index into that vector, that means you are trying to point to one element of that vector. Then j must be an integer, a whole number, in the range 0, 1, 2, ...., and it cannot have units.

Now look at how you defined j: it runs from Pp ( a few million Pascals) to sigma (I don't even want to know what that is.)

If you have to recreate the Mathcad file into Prime, be careful about what you change...

Success!
Luc