Alternative GL account not Changeable

Hi,

I have 3 chart of account in my company; Operating Chart of account, Group chart of account and the country specific chart of account. the country chart has been create after the company was already operative. Whenever we try to assign an alternative gl account in the gl master data, we getting an error message: FH007. If we assign the country account in OB62 there is no way to use an alternative chart of account in GL master. If we don't assign it in OB62, the alternative GL field is taking anything even alphanumeric values. The customer want us to put a validation so without assigning the country char of account in OB62, whenever we enter any other value than the alternative GL account number in the alternative gl fied in gl master data an error should be displayed. only values from the country chart of account should be accepted in the alternative GL field.

could anyone help please ?

many thanks