I'm using a formula to sum values in cells corresponding to time slots in the
day such as 08:00, 08:15 etc and have produced a macro to extract these
timeslots prior to using the formula.

Some of the source data, however, has errors and occasionally an additional
time slot will appear e.g. 08:00 where in fact 08:15 should be.

In order to accurately produce an error-free summary of the values at each
time slot I realise that VLookup could do what I want, but I'm not sure
exactly how to write the formula.

For example, if the data on my sheet was as follows:

Monday 3/1/05 08:15 456 (cell ref: F105)
Monday 10/1/05 08:15 789 (cell ref: F469) etc etc

and I wanted to sum 456 and 789 and all other values for 08:15 for January '05

1. what VLookup formula would I use to achieve this?
2. How would I then copy tis new total to a summary table in another sheet
on this Workbook?