I'm getting a Script failed error. I think this is because the Field name is on page 1 and the field with the calculation is on page 2.
The formula is just +Cash. I don't know how to tell it to look on Page 1. If I use the same field on Page 1, the formula works so I know it is not something in the field name.
This has NOT been answered
Page1.Cash should do it. If it doesn't, you could use CTRL+click to enter the name into your script.