How to make child table filed read only after save which are fill with data

How to make child table field read only after save that which are fill with data, but those field which are empty should not be read only.

This search may give you clues https://discuss.erpnext.com/search?q=field%20level%20permission

@clarkej; thanks for your command.

i search but i didnot fine my solution in that link.

I want child table field read only after save which are Entry data in field only.
below is child table field.
Eg. I entry data in ‘Goal’ and Weightage(%) field and I save. So i want read only this two field. If data is not enter than, this should editable not read only. Only after data enter in field it should read only.

Hii plz go to below link:
https://discuss.erpnext.com/t/how-to-change-set-df-property-in-child-table-field/3545/6

Hope this will help you.

@lokesh; thanks for command, but i didn’t got solution from this link.

Some suggestions here - dig around the code for ideas, and use an experimental trial and error approach to discover your answer.

Report what you find or the results of your trials so folks can then help you.