Changing cell colour based on another cell's value, but the latter cell changes

Hi all
Forgive me if this is a really basic formula but I'm trying to make a certain cell automatically change colour (to green) based on whether it meets or exceeds the value of a different cell. The reason I'm struggling is that the latter cell changes its value every few days so I can't put in a simple conditional-format.

In the example, the figure in C3 is my target, which changes twice a week.

The figure in F3 is the figure that I want to automatically highlight in green once it equals of exceeds that in C3.

Any help would be hugely appreciated....