Auto tab functionality

Hi Experts,

  In the CRM, I want to know How automatically the tab(Cursor) changes from one input field to another input field without pressing any key( enter or tab etc.) 

An example is given below in which the tab should change from phone field to pin field (after entering the input number 123456 ).

the size of the phone field must be 6 Chars only.

      Please help me how can i get this in CRM Code(Not in HTML Code).

    Thanks in Advance.

Regards

Srikanth