Help: how to use CAsyncCallBack

Hi,
i use CAsyncCallBack in my application,
but i cant delete the pointer in the disturct function.

----------the code----------
FuctionA()
{
TCallBack callback(CallbackFunctionPointer, this);
iAsynCallBack = new (ELeave) CAsyncCallBack(CActive::EPriorityStandard);
iAsynCallBack->Set(callback);
iAsynCallBack->CallBack();
}

~Application()
{delete iAsynCallBack;}
//if delete that pointer,system will show "cant find CAsyncCallBack"(maybe that means)
------------------------------

cant i delete that pointer in myself application?
system controls that? (ofcurse there are many asynchronous fuctions in the other applications)

Thank you so much !