How can you autofill conditional formatting on Google Sheet with data anchored on one cell?

Question

I have conditional formatting on cell B2 based on data in cell B100. ex: Custom Formula is

=B2>B100  

I would like to autofill conditional formatting for all subsequent cells in column B based also on B100. ex: Custom Formula is

=B3>B100
=B4>B100
=B5>B100
ETC

ALSO, would like to autofill the same conditional formatting across other columns. ex: Custom Formula is

=c3>c100   =d3>d100
=c4>c100   =d4>d100
=c5>c100   =d5>d100
ETC  

I want to autofill this conditional formatting so I don't have to do each cell by hand; I have about 450 cells I want to apply this formatting to.

Answer 1

Conditional formatting can be applied to a range. Write the custom formula as it should work for the upper left corner of the range, using relative and absolute references as needed (=B2>B$100, given by Scott Craner in a comment).

When this formula is applied to, say, 7th row, it will work as =B7>B$100.