how to avoid a leave event after it is called

Question

hello,
im looking for a solution with a slight problem that im sure it is possible, but i cant find anything about it on the web.
In my code, im calling a leave event out of a control that check's if the control has made any changes (txtBox, combo Box...) raising a question telling the user that changes weren't saved.
if the user click's on Cancel button, i want him to stay in the control and not actually leave like he initially did.
How can i do it ?
Thanks

 private void TabControlChars_Leave(object sender, EventArgs e)
        {
            DataTable charChanges = null;

            if (charsTypeDT != null)
            {
                charChanges = charsTypeDT.GetChanges();
            }
            else if (charsDT != null)
            {
                charChanges = charsDT.GetChanges();
            }

            if (charChanges != null)
            {
                DialogResult result;
                result = MessageBox.Show("Changes were made without saving !!\n"
                               + "All Changes will be lost ...", "Warning", MessageBoxButtons.OKCancel, MessageBoxIcon.Warning);
                if (result == DialogResult.Cancel)
                {
                    ???
                }
            }
        }