|Look at Conditional Formatting.|
I don't have 2007, so I can't guide you through the menus, but I can offer the formula to use.
First - a caution:
You said "...enter a word into A1 that if true"
The word TRUE is a reserved word in Excel and can cause problems when used in a formula.
For example, if you use this as a Conditional Formatting )CF) formula and enter Dog in A1, the CF will occur:
=IF(A1 = "Dog",TRUE,FALSE)
However, if you use this and enter True in A1, the CF won't ocurr:
=IF(A1 = "True",TRUE,FALSE)
This is because when you enter True, Excel assumes you mean the reserved word TRUE and not the text string True.
To make the CF work for True, you would have to enter a single quote before the word to tell Excel that the entry is Text. i.e. 'True
Finally, if you use =IF(A1 = TRUE,TRUE,FALSE), then entering the text string True would not be TRUE and the CF wouldn't work. I did not put quotes are the first TRUE, so Excel is going to assume I mean the reserved word TRUE.
For example, if I entered =B1=B1 in A1, then the result would be TRUE and the CF would occur.
Are you now TRUEly confused?