I would like to know if it is possible to change the imposition layout from going left to right, to down and over.

I am doing a data merge on to a tag that is 1" x 7".  The tags will be printed on to a sheet that is 11" x 17".  When I do the merge and use the imposition layout 3 across and 17 down.  The merge works with no problem, however the tags are shown printed as 1, 2, 3 on the first row and then the next row show 4, 5, 6 and so on.  I would like to have the layout as the first column going from 1 - 17 down, and then the next column starting with 18.  Thanks for all your comments in advance.