Option 4:
On Enter: ERASE another existing record.
On Delete: CREATE a new record or MODIFY an existing record.
On Replace: CREATE a new record then ERASE an existing record.

Option 3:
On Enter: CREATE a new record [or] MODIFY Fields in another existing record if a linking match is found.
On Delete: ERASE another existing record also.

Option 2:
On Enter & Delete: CREATE a new record
[or] MODIFY Fields in another existing record if a linking match is found.

Option 1:
On Enter & Delete: MODIFY Fields in another existing record if a linking match is found.

Option 0:
On Enter & Delete: MODIFY Fields in the current record.
This only modifies Fields that are not selectable on the current form.