Is there a way to do something like this:

select <Field1, Field2, Filed3>
from Table1
if (field1 = 6) then
where (Field2 between '3/1/2011' and '3/31/2011')
else
where field2 between '3-1-2012' and '3-22-2012')

I've tried this, and other variations (including When and Case), but no luck. I was hoping to do this to create a view.