Accessing one mathcad script from another

You would have to use "Insert"/"Reference" to achieve what you want.

While it is possible that A references B and also B references A, I wouldn't recommend it. If you use just the function cube() in the attached sheet B, then there would be no need that B references A.

So I would suggest to avoid circular references and that you put your calculations written as functions (like cube()) in sheet B and reference it at the top of sheet A, which takes the input values and uses the functions written in sheet B.

See if the attached would help - it still uses the circular reference which works, because of the very simple mechanism: whenever you insert a reference is is as if you would type the whole content of the referenced file in that position. So see yourself, insert the reference to B in sheet A a second time and look what the value of x is. The function cube() will be defined two times that way which does no harm.