Field needs to be filled by user for difference calculation

One word was missing from my formula. I overlooked it so many times. The formula is working now. User error...most definitely. Thank y'all for the help.

The screenshot at the bottom will show what I'm looking for, I hope. I did a formula prior to posting here and could not get it to work. 

The small column on the left is for Misc Expenses incurred and the Meals total is the top. All my auto calculations work except for getting the amount that is "owed" or needs to be "returned" to the traveler. So in my screenshot, all the variables are correct and in place to calculate that final number, be it positive cash (owed to traveler) or negative cash (traveler must return).

If this is clear as mud, please accept my apologies. Sometimes the smallest of things can cause the greatest of problems for someone, and I feel like that is where I'm at.

This is a simple calculation. With Acrobat JavaScript it is possible to perform much, much more complicated operations.

You can read about simple scripting for calculations here:

https://www.pdfscripting.com/public/How-to-Write-a-Basic-PDF-Calculation-Script.cfm

You're ("Cash owed toreturned") calculation script might look something like this: 

event.value = this.getField("Advanced Check Amount").value - this.getField("Total Expenses").value;

However, to get the calculation correct we'd need to know exactly what fields are involved and how. 

What is calculation?