Here's a question I answered for someone recently that I thought you all might enjoy. He wanted to have a query field showing the Year To Date totals for his sales:

You can use the DSUM function to generate a YTD total. If you don't mind changing it every year for the current year, you can just say:

Sales2012: DSUM("OrderTotal","OrderT","OrderDate >= #1/1/2012# AND OrderDate <= #" & Date() & "#")

If you want to use the CURRENT year, regardless of what year it is:

SalesYTD: DSUM("OrderTotal","OrderT","OrderDate >= #1/1/" & YEAR(Date()) & "# AND OrderDate <= #" & Date() & "#")

Hope this helps someone.