Try this:

=SUMPRODUCT(--([WorkBook1.xls]Sheet1!$A$1:$A$10=$A$50),--([WorkBook1.xls]Sheet1!$A$1:$A$10<=$A$51),([WorkBook1.xls]Sheet1!$B$1:$B$10))

HTH,
Elkar

"Will" wrote:

ok I cand understand the answers to other similar topics posted here so i am
going to have to try to explain my self...

I have two .xls sheet (WorkBook1 & Woorkbook2)

In Woorkbook1 on Sheet1 I have in column A incrementing dates...
In Woorkbook1 on Sheet1 I have in column B Total Run Time...

In Woorkbook2 on Sheet2 I have in cell A50 the START date...
In Woorkbook2 on Sheet2 I have in cell A51 the END date...

I am looking for a furmula that will sum the run time between and including
the START and END dates.

I have succeded in having the formula return a value for a single date but
not for the sum of the values found winthin a date range...