If you use Word for your input, the Shift-F3 routine will roll you through lower case, to initial caps, to upper case, and back to lower case.
You can also set, in Tools|Autocorrect Options, on the Autocorrect tab, to "correct double initial capitals" and "correct shift key errors." LOts of people seem to have a tendency to get "double caps" at the start of sentences. FOr most, it's sloppy keying, but of course in my case it's because of a defective SHi(f)t key.
If you use the shift key normally, but caps lock is on you'd get
iF YOU USE THE SHIFT ...,
in which case the "correct shift key errors" setting will automatically "reverse" the effect of the shift for what you've typed and will automatically turn off Caps-Lock, usually within two or three key strokes.