How do I make a multiple if statement in excel.?

Hello. I am trying to make a spreadsheet in excel 03 and I want to add two cells (D7 and D15) and input the answer in D21 IF A6 - A11 is greater than 2000 and less than 4000 . Also, in the same D21 cell I want to add D8 and D16 if A6 - A11 is more than 4000 and less than 8000. Is that possible?