if i want to time an operation, can i format the result from the start
time to the end time in seconds and fractions of a second, rather than
just whole seconds?

You could format your result as [s].000

thanks. don't know what i'm doing wrong, but when i set the start time to
now, and the end time to now and then subtract, i get something like this:
8.10185156296939E-05
when i try to format the output like you suggested, i get zeroes.

Well, the format that Ron gave you will only display 3 decimal places, the
number you posted is

0.0000810185156296939

with the power of 10 part multiplied through, which, if you notice, has 4
zeroes after the decimal point. That number, rounded to 3 decimal places is
0.