Crystal Reports 11 help! dateVar range array

I need help with crystal reports. I am extremely new to this and have been thrown in at the deep end with this. I am trying to create a report that selects 3 months from last year and then compare them to the same 3 months this year. I am using the dateVar range array formula but when i enter in this:

dateVar range array DateValue := [2006, 08, 01 to 2006, 10, 31, 2007, 08, 01 to 2007, 10, 31];

i get the error saying that a date array is required and selects everything in the [] I have never used Crystal reports. Its not greatly important as I can just export the whole thing into Excel and delete the months i don't need but well every little helps i guess. Any ideas?