Conditionally populating a control is done in the OnRow() method of the control itself. In your case, the date field.
Can you insert some code that test the value of the DataRow date field, against NOW() and only set the field if it's < NOW().
Pseduo
OnRow()
IF Not getvalue() < NOW() THEN ' Ensure formats are same
DataValue = Spaces ' DO not show date
END IF