It is not a good idea to make this in a synchronous way. If the process takes 1.5 minutes, it may likely timeout and it will also hold a slot for open requests on server.
You should initiate this action as asynchronous in a new thread, and display async log while this action executes. You can see some examples how this is done in Kentico UI code, e.g. \CMSModules\Content\CMSDesk\Delete.aspx, look for AsyncLog control (AsyncLogDialog) and actions bound to it. For further details, contact support or consulting.