Gopal Ramesh sent us a routine he uses to perform basic arithmetic functions in AutoCAD by selecting text he wants added or subtracted.
"This command, Txtcalc, allows you to perform addition and subtraction with AutoCAD text and dimension entities. The command sequence is similar to that of the Area command of AutoCAD. On entering the command, it will show the current total as 0.0 and then choose the mode Add / Subtract. Both options will prompt you to select objects. You can select multiple objects at a time and the program performs the selected arithmetic operation on the selected entities and shows the new current total. You can continue with the desired option or type X to exit to show the grand total and exit the program. This program is very useful especially with dimension objects and it takes care of both default and overridden dimension text."
Notes from Cadalyst Tip Patrol: This is a handy routine that is easy to use, and very quick. The subtraction is tricky in that you have to keep telling it that you want to subtract, not add. Also, if you dimension, or annotate in feet and inches, the routine can’t handle the inches. It adds the feet, but seems to ignore the inches. Decimals work great, even in associative dimensions.