Hi Sean

this formula should do what you want, but only if the Dates are
sorted:

=SUMIF(INDIRECT("C" & MATCH(SheetB!A2,B:B,0) &":C"&
MATCH(SheetB!B2,B:B)),SheetB!A1,INDIRECT("A" &
MATCH(SheetB!A2,B:B,0) & ":A"& MATCH(SheetB!B2,B:B)))

Although the cells you posted for your dates in Sheet B are the same
as your word. so I changed them to
Word: SheetB!A1
Date1: SheetB!A2 (First Day for lookup)
Date2: SheetB!B2 (Last Day for lookup)

I don't know how you could solve it if the dates are not sorted.

Hth

Carlo