If i have a table with these fields in sql express

Date Pay
28/03/2012 100
30/03/2012 300
02/04/2012 1500

Today lets say is 02/04/2012. I want some help to do the above:

For example i want to take all the pays of the previus month and bring the total. I want to write some code so the crystal reports understand and what day we have today go on previus month and take the total of the pays of previus month.

For example the result will be paylastmonth:400