How to create multiple unittest reports by executing each unittest only once?

Question

I need multiple output formats from my unittest cases..

1. HTML output
2. XML output

Currently I need to execute all test cases multiple times with

1. HTML Test Runner for HTML output
2. XML Test Runner for XML output

This is because result object is bound with each TestCase and I couldn't found how can I bind list of result classes to each TestCase...(which may actually solve my problem)