Set polyline elevation

Hi guys,
I create contour line in TOPOGRAPH program, and I import these polylines to AUTOCAD.
I have to set elevation for each polyline manually, and I waste a lot of time doing that.

So I come here to beg for help, if someone has a lisp doing that automatically.
I mean, invoke the command, set the first elevation and them select the polylines.

e.g. The first elevation is 530. The next polyline that I select is 531 and so on.

Can anyone help me please??

Thank you very much.