Highlight cells in column A if same value found in column B

Hi,

I'm trying to simply highlight cells in column A if the values in column A match the values found in column B. So if A contains the number 150, and B contains 150 also, highlight the cell that contains 150 in column A.

I tried using conditional formatting, highlight equal to value and with the following formula: =$B$1:$B$100.

However, this doesn't highlight anything.

What's a good approach to this?

Thanks!