how to find overall min-cut separating some node pairs, not all node pairs

[shaon]

As we know, now there is efficient algorithms to find the overall min-cut in a directed graph, e.g. Hao and Orlin (1994).

Now my problem is to find an overall min-cut just separating some given node pairs, not all the node pairs. For example, I have an 8-node digraph with capacities on each arc and want to find the overall min-cut separating only some node pairs such as 8 and 1, 6 and 3, 7 and 1.

The algorithm of Hao and Orlin (1994) cannot solve my problem.

Thanks a lot.

Shaon