Browser redownloading tiles when returning to zooms anterior...

[Etides]

Hi,

    I have an Openlayer site that use Tilecache to generate tiles from a WMS on IIS... When returning to an already visited sector of the map, Tilecache is always downloading the same tiles again and again... I heard that there is a way to force the client to reuse the tiles already downloaded with Apache mod_expires but  i'm looking for a solution working on IIS...

Any suggestion?

Thanks a lot

Etienne