Thanks Jeff, that's a good work-around and beats adding a second upload control for just that one thing. :)

I'm assuming since you are suggesting to use server-side code, and thus a post back, thatthere isn't away to do this on the client-side via script, correct? If that's the case, I'll probably go down the road of two upload controls instead.... what a shame though!?  

Now, I have the opposite problem... when user needs to upload multiple files, in the OnBrowse event I change this.internalobject.MultipleFilesUpload = true;  And now the dialog won't allow the user to select multiple files.... see event code below to show what I'm trying to do... function ...

I have an upload control that is contained in a jQuery UI dialog.... users are allowed to upload multiple new files, or change/update one file at a time. So the control starts off allowing multiple files to be uploaded. But if the user wants to update an already existing file, they need to be restricted to only selecting one file. I  ...