Freeze Change in Key Figure for first 3 months

Hi All,

We have a requirement wherin we need to make the Key Figure uneditable/read only for the first 3 months. So if we are in jan month, then users can not change values in the months Jan, Feb & March.

Through EPM sheet options, we can free the key Figure for the whole time period but not for "part" of the time period.

Can anyone please share some information/solution on how to acheive this freeze ??

Regards

Abhishek Sahi