Open Item Management Activation for Existing GL

Hi,

exisiting Gl shold be convert in to Open item management with each line item should show as the open item or cleared after convert into that gl. but if we use FAGL_Activate_OP, its show as all are cleared item only. how can i convert into my requirement ?

or i have idea, is it correct or wrong plz clarify me.

IN SAP two type of data is ther for taking downtime. when we take down time first upload the master data ,

after that can we change in fs00 as open item for each gl what ever we required.

then can we upload the master date ?

then the system will considfer this is as open item ? or any problem we will face in futture ? plz clarify me .

Prince