Erpnext custom doctype

[amal_31845]

doc.custom_approval_status == "Pending Approval" 
|| doc.custom_approval_status == "Account Manager Approved" 
|| doc.custom_approval_status == "Customer Support Approved" 
|| doc.custom_approval_status == "Production Approved"
|| doc.custom_approval_status == "Approved";

Here

Pending Approval
RM Approved
Account Manager Approved
Customer Support Approved
Production Approved
Approved

these are the options in custom_approval_status
i want to make that field only editable when the custom_approval_status has the value RM Approved how can i achieve that all the other options the field should visible but wake readonly

[NCP]

Please add eval.

eval: doc.custom_approval_status == "Pending Approval" 
|| doc.custom_approval_status == "Account Manager Approved" 
|| doc.custom_approval_status == "Customer Support Approved" 
|| doc.custom_approval_status == "Production Approved"
|| doc.custom_approval_status == "Approved"

[amal_31845]

It is getting hide i want to make it readonly

[NCP]

If no value then it’s become hidden.