How to make name value pair field read only ?

[Shreya Nagar]

Hi , 

I have tried onChange client script when field value is changed then name value pair field will be read only but after form has been submitted then field will be non read only , I have also tried UI Policy and Dictionary but it also not working , Please let me know .

[Anurag Tripathi]

how are you using the code ?

and how are you testing