I can open multiple Excel workbooks sequentially. I can even open the same Excel document twice in the sample application. I also found that the Excel process in background is still running and not terminated actually after I close the Excel from within the sample application. The toolbar in the Excel will be freeze up while switch to new Excel window.
This article explains how to host multiple Excel documents in a form or multiple tabs programmatically.
Firstly, please make sure you have installed Edraw Office Viewer Component V7.x. If you haven't got the version, please download it here.
Then the following example will demo how to open two more excel instances at the same form using VB.NET.
Run the project, you can see the result as follow.
If you want to put the component in multiple tabs, you can only use an Edraw Office Viewer Component. Put it in the form. Then call the Open method. The component supports the IE7 and IE8. You can also host multiple Word Instances in the same form, too by this method.