Unable to stop outlook to sync with IMAP account

[Stop method of Sync object is not workin]

Hi All

my outlook profile handles two accounts one is of exchange and another one
is of IMAP. Out of these two accounts I want to sync with IMAP account in
certain cases only(like when system is idle or when exchange is offline)

For achieving this I have created an Outlook Add in that handles Syncstart
event, when sync start is fired I am just stopping that by Stop() method of
Sync object.

I have tried below code but was not able to stop the sync. Can anybady help
me on this.

private NameSpace ns;
ns = ThisAplication.Session;
private Microsoft.Office.Interop.Outlook.SyncObjectClass mySyncObject;

public void OnStartupComplete(ref System.Array custom)
{
mySyncObject = (SyncObjectClass)ns.SyncObjects[1];
mySyncObject.SyncStart += new
Microsoft.Office.Interop.Outlook.SyncObjectEvents_SyncStartEventHandler(mySyncObject_SyncStart);
}

private void mySyncObject_SyncStart()
{
ns.SyncObjects[1].Stop();
}

Thanks in advance.