best way to take backup for old partition and create new one?

[Aamir Sohail]

I have a MyISAM table with 10 partitions weekly(for two months), but after two months-

1. I have to take backup of oldest one.

2. Drop that partition. --I can use drop(no problem here)

3. Create new partitions.
Each partition contains 16,800,000 records. How much time this 3 step gonna take?

What is best way I can achieve this. Is it possible to make some schedule for automatically perform all 3 operations.

Thank you.