How to make a date cell turn red

[Snaggles]

Hope someone can help with this, before I lose the rest of my hair!

Using Excel 2007

Cell F20 contains ='book 3'!C11
The cell is is formatted as a date and simply reads the date from the other sheet.
I want to make cell F20 turn red if the date is over 30 days ago.

Sounds simple for conditional formatting, but I just can't make it work. There must be a simple way to make the cell turn red if the date goes over 30 days.

Help please!!

TIA

[NBVC]

Choose to format only cells that contain...

and then choose Less than and enter =Today()-30

It cell F20 could be blank, then you can choose Is Between and enter 1 and =Today()-30

[Snaggles]

Brilliant... that works!!

I was close, but hadn't included the ().

Many Thanks.