Auto-Enter the next date in a portal?

[db dummy]

i'm building a database for touring bands... each record in the database is a specific show date. right now, i have a portal that shows related records by Artist, filtered by Status (whether the show date is confirmed or not confirmed) and by Date. the user enters in the range of dates to be shown

here's the tricky part (tricky for me anyway)...

as the user tabs through fields in the portal, i would like the new records that are created to auto-enter an increase in the date by a value of one day, using the previous portal row as the reference. for example, if the last portal row being displayed has a date value of 12/04/2004, i want 12/05/2004 to automatically appear when tabbing through to create a new record. i would like this to modifiable, in the case that there is a day off between shows, etc...

i've tried a couple of different calcuations to auto-enter this stuff, but i'm still not too familiar. please forgive my ignorance in these matters - found a lot of help in these pages and hoping someone might have a tip.

thanks for reading this far!

[-Queue-]

In the related file create an auto-enter date calculation of Last(selfrel::date) + 1, where selfrel is a relationship from ArtistID to itself, sorted by date. You could also use selfrel::date + 1, where selfrel is sorted by date descending.

[db dummy]

so i created a new relationship, with the table dates relating to itself, named the new occurence selfrel, entered the calculation to the field Date, and no dice... could it be a change that's been made in filemaker 7?

i've attached the database here, if anyone would like to mess around with it

AeroBooking.fp7.zip