U should use activex components to run a dll @ client.
For office specific, u can use microsoft office web components...

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HTH
Thanks,
Yunus Emre ALPÖZEN
BSc, MCSD.NET
> Am desigining web application and I have a dll that perform operations on
> excel object, how can i run this dll on the client machine so it uses the
> clients' excel in its operations ?
> how can i download this dll on the clients machine and run it ?