Solver - Set changing cells to be unique

I am trying to use Solver to derive an optimal ranking of a list. I believe I can do this by a) setting each changing cell to be an non-negative integer b) set the sum of the rankings to be equal to the sum of the number of items in the list and c) setting each changing cell to be a unique value. I am struggling with how to set each changing cell to be a unique value. Does anyone have any thoughts?

If you are running Excel 2010 you have the option to set "Cells to change" to "dif" i.e. "AllDifferent"

http://www.solver.com/content/basic-...affect-solving

Alf

Thanks. I eventually found the dif option. However, what I've also found is that my list of items (approximately 150) is too big to be sorted by Solver. I would like to try sorting only a subset of it (say items 50 to 65) and seeing if that subset of the list in in the optimal ranking but since the dif option check tries to ensure that the list is unique from 1 to N (as opposed to checking for unique values from 50 to 65), it doesn't seem like Solver is going to be a viable approach for this task.