Hi,
In the merging process, as reported above, no, you can not.
But, for a route in preparation for merging, Yes, you can.
But, it either cost money or you need a friend who has spent that money.
Check out TransDEM in the payware part of the forum, it can help with raise and lower a route.
May not always work perfect, but it can be done. There is also some threads about this before floating around in the forum.
Linda