Selecting data from current date and previous 2 days

Hello,

I have just started using CP in a healthcare setting.  I am trying to put a report together to track patients' lab values from the date the report is opened and the previous 2 days, which will give me 3 days worth of lab values.  The results come from a data field called, CollectionDate, and all I want to do is limit that to the current date and previous 3 days.  I have found a standard function for this in CP called Last7Days, which works great but I only want the last 3 days of data.  I am sure this is a rookie formula, but I have just started using this program.  Please let me know if you can help.

Thanks,

George