How to add sent item handler to the opened outlook form rather than to the entire application using C#?

See more:

Outlook

Hii friends,
I am customising my outlook. I have created my outlook addin and added an custom button which when clicked opens up an outlooks new mail form using the below code.
Outlook._MailItem oMailItem = (Outlook._MailItem)oApp.CreateItem(Outlook.OlItemType.olMailItem);
oMailItem.Display(true);

Now, I want to capture the send item click event and do some operations only if the user opens up a new mail form by clicking on my custom button, rather than opening directly a outlook new email button in the tool bar.
Outlook.Application oApp = new Outlook.Application();
oApp.ItemSend += new Microsoft.Office.Interop.Outlook.ApplicationEvents_11_ItemSendEventHandler(OutlookApplication_ItemSend);
The above code helps me to capture the send item click event when placed in ThissAddin.cs , but it also runs for entire application whenever the user click on the send email button which I should not allow.
Can anyone help me with how to acheive this ?
Thanks in advance.
T.Sudhir

What I have tried:

Outlook._MailItem oMailItem = (Outlook._MailItem)oApp.CreateItem(Outlook.OlItemType.olMailItem);
Outlook.Application oApp = new Outlook.Application();
oApp.ItemSend += new Microsoft.Office.Interop.Outlook.ApplicationEvents_11_ItemSendEventHandler(OutlookApplication_ItemSend);
oMailItem.Display(true);