I am having a problem in writing a function for a multiple spread sheet
workbook that involves dates, qty, and customers. What I what to do is type
in a date range (beginning in one box and ending in another) to produce a
listing sum of the qtys by customer.

This is what I have but I am not doing something right.

=SUMIFS('Master Listing'!D:D,('Master Listing'!N:N,"="$N$35,'Master
Listing'!N:N,"<=$O$35"),'Master Listing'!C:C,B6)