I need to do a find and replace on all single spaces after periods, and
replace with two spaces. The problem, of course, is that if I do just a
straight period-space conversion, I will include the places that already have
a period and two spaces after them (with the find just ignoring the second
space in its search).

How can I indicate that I only want it to find periods with a space and some
character after the space, as the find criteria? And then also importantly,
how do I tell it to replace the period-space with period-two space, and then
leave the character untouched?

Thanks.
--
Boris