Just select all the
rows you want to apply it to first, and then lock down the column reference in the formula.
(Be sure to write the formula as it applies to the
first row in your selection, it will adjust for all the others).
So if you wanted to apply it to rows 2-100, select rows 2-100 (the entire rows), go to Conditional Formatting, choose the Formula option, and use this formula:
Placing the "$" in front of the column letter "H" locks it down, so every cell is looking at the value in column H.
Not placing the "$" in front of the row number allows it float, so row 2 will look at the value in H2, row 3 will look at H3, row 4 with look at H4, etc.