Conditional Formatting with a text string

I am trying to use the conditional formatting feature (of Excel2002) to highlight cells which contain a text string (in this case a last name) from a drop down list I created.
For example, if I select the name "Monroe" from the drop down list, all the cells in my conditional formatting range that contain only "Monroe" in the cell turn green as I want. (I used the cell-- is equal to command in the conditional formatting box). But when the cell contains more than just "Monroe" such as "Monroe/Smith", the cells do not get highlighted. How do I get the conditional formatting to apply to every cell that contains "Monroe" regardless if there is more in the cell or not?

Thanks for any help with this matter.