Reload IFrame from Code Behind (when aspx opened as modal dialog)

[Guadala Harry]

I have an aspx page that opens as a modal dialog. The aspx contains two
IFrames (ID = thumbFrame and mainFrame). From the code-behind of the page
that loads in mainFrame I want to cause the page that appears in thumbFrame
to reload.

I have the following code that works fine with a normal frameset (no
IFrames) that is NOT opened as a modal dialog. It fails with IFrames. What
needs to change now that I have replaced the frameset with IFrames?

string scriptString = "<script
language=JavaScript>parent.thumbFrame.location.reload(true)</script>";
if(!this.IsClientScriptBlockRegistered("clientScript")){
this.RegisterStartupScript("clientScript", scriptString);
}

Thanks!