Access 97 form troubles

In a form, in ‘add mode’ I want a bound text box to have a default value as follows:

Max[textField]+1

textField contains only numbers.
Add mode doesn’t cycle records(for me anyway.
If the value is obtained from another form, default value isset before the other form has finished calculating.
A ‘set value’ macro doesn’t want to work on my ‘bound’ text box.
textField has values from another form also, can’t be auto number.
Database tables are in a MDE from the previous programmer who has conveniently lost all source code and we need to make a whole new dbase system for the changes we’re incorporating.
This form will determine the next ‘job number’ and allow manipulation of accounts to describe what the jobNum is.