Adding a field to a report footer

[Porky]

I am running a report based on a single table. The table relates to payments made both in and out. It includes things such as Total Sale, Cash, Card etc as well as till total carried forward (The report is based on a single week and so the user inputs last weeks closing balance, I am sure it could do that for me but I am not that Advanced) I have in my report footer calculated fields such as totals for cash etc which work fine. I want to put into this footer a field from the main body which indicates the true total in the till, again entered manually, but as this report will be run every day and as it is a weekly report i want to lookup the value of the last entry by date or payment ID (autogenerated) I guess i could use DLookup, the field is "ActualTillTotal" the Table is "Payments" What would you suggest i use for a DLookup? or is there a better way?