Default Value in Access 2000

Can anyone tell me how I can set the default value of a form field to be the value of another field on the previous record?

e.g. record 2 [start time] = record 1 [finish time], record 3 [start time] = record 2 [finish time]…and so on.

All Ihave managed to do is use the default value property but this sets it to [finish time] on the current record.

Also, how can I use the Sendkey function to send CTRL+ALT+SPACE to update the field automatically when the field is entered?