Need to Hide '+' sign on a subgrid using JS code if a particular condition is met.

I have a subgrid and 8 tabs on the form having different number of sections on it.

When I completed filling the 5 tabs and as soon as the BPF flag is set then the '+' button on the subgrid should be hidden for particular user role and also the records in it must be readonly.

Please help me to achieve this.

Thanks in Advance.