Hi, Judy.
The more simple would be park a manual document by FB50 or FV50 as Sanil said above.
I would also suggest you to investigate the use of Manual Accrual Engine (ACACTREE01) in FI-GL.
It requires a little configuration but its a simple tool that creates in advance a package of planned accrual documents for a entire period (a year or more if you want).
There is also two reports that helps a lot.
For me its worthwhile.
Best regards,
Nilton Duque.