need to chart sum of 2 rows in worksheet

[BCS]

I have a worksheet in which I have 12 columns to represent the months and my
expense categories in the rows below. The last row is a Total row of all the
expenses above it. One of the values I want to represent in a 12-month line
graph is the Total row less the Misc Expense row. How can I graph this
without creating a new row in my worksheet to hold just this calculated
value? I'm very comfortable with writing macros if that's what it will take
to accomplish this.

Thanks,

Barry