I have a spreadsheet which is as follows:

NAME DATE OFFENCE
J.Smith 1-Jan-05 eating
M.Patel 9-feb-05 drinking
T.Pot 11-mar-05 eating
E.Colin 13-dec-06 eating
A.Idle 6-apr-06 eating

I want to calculate the amount of times 'eating' occurs between 1-jan-05 and
11-mar-05. I've tried a formula which counts the occurences between a range,
but because there are 'sort' buttons over name, date and offence and the data
shifts location each time a user 'sorts' something, my figures are no longer
accurate. Please help!