SQL Server Admin 2014 :: Backups To Different Folders Based On Week Day

I am trying to create a job that would backup a DB dynamically to a different folder based on the week day. So if it's Saturday, backup to folder Saturday.

I have this

DECLARE @BackupLoc nvarchar (100)
DECLARE @DayOfWeek nvarchar (100)
set @BackupLoc = N'D:Backup'
set @DayOfWeek = (SELECT DATENAME(dw,GETDATE()))
set @BackupLoc = @backuploc + @DayOfWeek

[Code] ....

But it's giving me permission errors, although the AGENT and MSSQL service accounts are members of the local admins group.