Creating a Text box that calculates a sum.

I’ve created a database, 1 table has VesselIDPK, date, tank name (e.g. 1, 12 Mar 2007, Pacific Princess), tankTypeFK and the other has TankTypeIDPK, type (e.g. 1, Small, Large, Medium). They are related so it shows for each VesselIDPK this is the type of Tanks.

I’ve created a report that pulls out the information and lists it by VesselIDPK, date, tankname, type. Each month is on a different page. It works but i want to put a calculation (via text box) that says for this month – we had 4 Small Vessels, 12 Medium, 13 large.

How can I write a code that will allow me to total that information? Or is there some easier way to state it in the report.

Urgent, need help and thanks.
Dyna