Double Question: (1). How do I zero a record count? (2) How do I implement a count based on a mask

Hi
A long long time ago, I wrote an access database (Access2) for a colleague who's partner was a plumber. Since then I've got older, MS Access has changed but someone else would like a copy of my database.

There are Three tables

Table 1 Holds all the forms, reports and coding etc
Table 2 Holds all the Servicing periodicities, Servicie Type & VAT (Tax) rates;
Table 3 Holds Customer Details; Client Accounts Invoice details etc

I have, I think managed to convert to and Access 2000 database  ormat and surprisingly all my macro's and functions appear to work in the new format!

I have changed all the titles and report names to reflect the new business name but there are a couple of additions the new guy would like, don't they always?

1. How do I zero the underlying record count so that when I have finished designing and testing I can put everything to zero and ship a clean database.

2. My new "Client" would like to display Job Number and Invoice number on the invoice, How can I create a field that will show an incremental number which would be part of a mask
for example Job No = RWTB040404001 040404 = ddmmyy 001 = incremented number
                  Invoice Number 111 = incremented number

I know that I can use the autonumber facility but I already use this in the tables to create the unique key reference so don't think I can use the function more than once in the same table so think I might have to call a function but how to make it work?

Finally. OK I know I said 2 questions but I'll make it worthwhile How do I switch off the macro warning that pops up everytime I open the database?

Look forward to hearing your suggestions

Mike