Excel 2007 : Recurring Amount

List the dates down a column:

      ----B---- -C-- ---------D----------
  2     Date    Amt                      
  3   6/1/2011   350 C3: Input           
  4   7/1/2011   700 C4 and down: =C3+350
  5   8/1/2011  1050                     
  6   9/1/2011  1400                     
  7   10/1/2011 1750                     
  8   11/1/2011 2100