Problem while Creating Folder in Mapdrive

Hi All,

   how can i create the folder in the mapdrive using c# in windows application..

i.e

txtDesPath.Text = "Z:\"

System.IO.Directory.CreateDirectory(txtDesPath.Text + "RXLFTPBACKUP\\");

it's gives the Error Message like "Access to the path 'Z:\RXLFTPBACKUP\' is denied."

Thanks in Advance