Copying formula where one referenced cell must remain constant

In it's simplest sense what I want to do is copy the formula for C1, A1-B1, straight down the C column so that the result is A1-B1, A2-B1, A3-B1, etc... The problem however is that if I grab the corner of C1 and drag it down the column, the formula becomes, A1-B1, A2-B2, A3-B3, etc... How do tell the formula to stayed fixed on B1 while A increases in each row?

Change your reference from B1 to $B$1.

Oh that is beautiful! There is no way I would ever have figured out that bit of code. So happy for this forum!

Happy to help! Don't forget to mark the thread as solved!

~Cheers!