Hi @Kesh ,
Do you want to create a Business Rule for your custom Entity to fill "Name" field with concatenated three fields value?
If you want to create a Business Rule for your custom Entity to fill "Name" field with concatenated three fields value, I afraid that there is no way to achieve your needs in PowerApps currently.
Within Business Rule, there is no function or operator supported to concatenate multiple fields value for one field in CDS Entity.
As an simple solution, I also think the Calculation field functionality could achieve your needs. You could also consider remove the "Name" field from your CDS Entity, then configure it as a "Calculation" field as below:
More details about the Calculation field in CDS Entity, please check the following article:
https://docs.microsoft.com/en-us/dynamics365/customerengagement/on-premises/customize/types-of-fields
Then you could use the CONCAT function to concatenate multiple field values (including LookUp field value) as below:
Within the expression box, type the following formula:
CONCAT(name, "-" ,accountnumber, "-", primarycontactid.fullname)
on your side, you should type following:
CONCAT(user.fullname, "-" , year, "-" , week_number)
Please consider take a try with above solution, then check if the issue is solved.
In addition, I also think the the Workflow functionality could achieve your needs. Please check and see if the following blog could help in your scenario:
https://powerplatformramblingsbystevenblog.com/2012/05/22/how-to-concatenate-two-fields-using-workflow-in-dynamics-crm-2011/
Best regards,
