you can take cdg-dbrt 15904 from chandigarh and reach new jalpaiguri. here you can get toy train for darjiling. remember this train 15904 runs only on tuesday from chandigarh. another option to go to delhi/new delhi where you get many northeast bound train like 12522 northeast exp./12424 rajdhani/ 14056 brahamputra mail and many other trains to njp.