Hi,
In projects I want to create a field “End Date” and it must be mandatorily filled before marking the status of project to completed.
In case i check the box “is mandatory” I will have to fill it in the beginning only, but I want it to be filled compulsorily before completing the project.
You may have to write custom script to achieve this. Check the following https://erpnext.org/docs/user/manual/en/customize-erpnext/custom-scripts/custom-script-examples