Why not fill the missing dates in column 2? An easy way is to highlight column 2, then press F5 (GoTo), then click Special, and then click Blanks. Then begin to enter a formula by typing = then click in the cell above the first highlighted cell (i.e. B1 in your example) and then hold down the CTRL key and press Enter. Then you can enter this formula in C1:

=IF(C1=C2,"",SUMIF(B:B,B2,A:A))

then copy down. Your subtotals will appear on the bottom row of any blocks with the same date.

Hope this helps.

Pete