stop pivot table from inserting zeros for blank values

I have a data set with three columns: date, percentage return, and a binary (0 or 1) variable describing whether an event occured or not.

e.g

Date, Percentage Return, Event
1/1/10, 10, 0
1/2/10, 9, 0
1/3/10, 15, 0
1/4/10, 25, 1
1/5/10, 7, 1
1/6/10, 13, 1

I created a pivot table that has dates in the row, the binary variable in the column, and percentage return as the value fill. The pivot table lists each date consecutively and the percentage return in on of the two columns depending on whether the the return for the period was associated with the 1 or the zero. For example, the return for 1/1/10 would be in the 0 column, and the return for 1/14/10 would be in the 1 column.

In the 1/1/10 example the pivot table would fill the 1 column with a zero value. That is my problem. I need the table to return a non value, blank cell. Currently my calculations based on the pivot table are skewed towards zero when the zero value is inserted in place of missing data.

Any help would be greatly appreciated!!!

Thanks
cornman