Restrict the movement of Tab key in only dhtmlx child window

A dhtmlx window pops out of normal parent window. Now when Tab Key is pressed in the dhtmlx window, after covering all the fields in dhtmlx window, the cursor moves back to the parent window. How can we restrict the movement of cursor using Tab key in only dhtmlx window, that is the cursor should not get tabbed to the parent window.

dhxWindows component doesn’t provide ready solution for such a restriction

Please suggest some alternative to achieve the same. If we Tab on a normal child window, Tabbing will not move back to parent window after finishing the cycle. In the normal child window Tabbing is restricted only to child window. Please help to achieve this in dhtmlx child window.