Sharepoint calculated column help- absolute values?

Hi, 

I want to create a calculated value in my SharePoint list, based on 2 other columns; in a previous excel document I have used:

=IF([@[Response On Time]]=$AV$2,"On Target",IF([@[Revised Response On Time]]=$AV$2,"Within Extension",IF([@[Revised Response On Time]]=$AV$3,"Out of Target","Out Of Target")))

but that was using absolute values. I can't see any way of creating absolute values anywhere in the SharePoint list to refer to, but do I actually need to? Can I not just change the absolute value reference ($AV$2) to a Yes/No as specified in the columns i'm using- why won't that work? It won't, i've obviously tried it, but I don't understand why, or where i'm going wrong with the whole thing. Any help would be gratefully received, thank you!