Need to change "Data Conversion Level" from "Journal Level" to "Subledger Level" on Secondary Ledger

Hi, I created secondary ledger with "Data Conversion Level" set to "Journal" instead of "Subledger" at the time of creation of ledger. Now it doesn't let me change the flag to "Subledger", so that I can assign my Subledger Accounting Method.

Can someone please tell me if there is a way to change that? May be a script which you allow to chage the value of Data Conversion Level?

Thanks,