marlea wrote...
....
I want to place a colon after the numbers; e.g., R1: volume...; R12:
height. If I knew how to find the first occurrence of a space, I think
I could just find those spaces and replace them with a colon and a
space. My work-around is to use REPLACE this way:

I apply this formula to cells with one-digit numbers:
=REPLACE(A1, 2, 1, ":")

Then I slightly change the formula for cells with two-digit numbers:
=REPLACE(A1, 3, 1, ":") ... and so on.

Can someone show me a better way of doing this? Thank you!
....

If it's always the first space you're replacing, don't use REPLACE, use
SUBSTITUTE.

=SUBSTITUTE(A1," ",":",1)