Unit cost planning month Wise Issue

Hi,

After performing Unit cost planning in T.Code CJ40. I Checked Elemental Overview where system has distributed total value in 12 periods.

Now, I want to do planning for 4 periods only, system usually doesnt change it.

Please help how to do same.

Ex Plan amount is 12000

Month wise equally distributed Jan-1000

Feb-1000

March-1000 and so on

But I want to change it like
April-3000

May-2000
June-7000
No planning in Jan feb march and july to August

How to Achieve same?

Thanks

Rahul