I have one Add-in (Siebel), thru which I get 1 toolbar and also some Siebel
links. This add in only developed to work with contacts, Tasks and Calendar
but I need same toolbar when I open new mail and it should work.

My question is:
Should I use VBA for extending that add in or should I use COM
interoperability thru .net. Please suggest me.

Points:
*) I don’t have that add-in source code
*) That Add in is given by Siebel