How to Union while using Function?

I Have List of Company ,i need to union to display all Company as select all how can i achieve this i have code below:

(SELECT CompanyID FROM dbo.HRMEmployeeMaster WHERE dbo.FunctionGetCustomFieldValuebyJobIDFieldNameandDatatype(Job.ID,'EmployeeName','StringValue')
                                  = ((CONVERT(Varchar(MAX),EmployeeId)+'-'+Name))) = @CompanyID