Subtracting one variable value from another to create a third

[#1]

I have written an expression in the load script to create a variable called NLLOS. The expression is:

IF ([DC_DESTINATION]<>'63', LOS,0) as NLLOS

DC_DESTINATION and LOS are in one table.

From another table I load a field called GLOS.

I add all four fields to my TABLE object.

I want to create a fifth field that will subtract GLOS from NLLOS to create a field called NLMN if DC_DESTINATION <>'63'.

What is the syntax?

Thanks

Glen P.

[#2]

Can you show the script?

[#3]

Here is a copy of my file.

Thanks

Glen