Sum total of all cells between 2 HLOOKUP points

I'm using a bit of clunky large spreadsheet that contains various metrics broken down daily for each day of the year.

I've created a worksheet that pulls that information into one place use the HLOOKUP function by allowing the user to enter the date they want and returning the corresponding metrics for the day.

=HLOOKUP($B$1,RESULTS!$CE$5:$QD$63,3,FALSE)

What I'm stuck on, is getting SUM of that same information, using two date points entered by the user. In this example if date 1 is in $B$1 and date two is entered into $C$1 - how would I add the value of those two dates and every date in between?