How to display confirmation message in SPItemEventReceivers

Is there a way to display confirmation message in ItemAdding event?
I would like to display confirmation message and based on user input proceed with the other steps.

public override void ItemAdding(SPItemEventProperties properties)
{
  // Display confirmation message
  if(OKClicked)
  {
 // Do something
  }
  else
  {
  // Cancel Operation
  }
}

Thanks in advance,

dhijit