Hi Leanne99,
You are following the right steps, instead of "f13=first aid" enters the below mentioned formula:
=ISNUMBER(SEARCH("first aid",F13))=TRUE
For step by step help on this, in your reply, please mention the version of Microsoft Excel you are using (such as Excel 2003, 2007, 2010, etc.)
Please do write back to us.
Thanks & Regards
Zohaib R
#iworkfordell