How to combine onclick's

In my Page_Load() I have the following code:
Button btnCancel = wizSummaryDetails.FindControl("FinishNavigationTemplateContainerID").FindControl("CancelButton") as Button;
            btnCancel.Attributes.Add("onclick", "setSessionAction('NONE');"); 


Also, I have the following function that handles clicks on the same button:
protected void DetailCancelButton_Click(object sender, EventArgs e)
        {
            wizSummaryDetails.MoveTo(wizStepSummary);
            Session["Action"] = ACTION.NONE;
            LoadData();
        }
But if I have that part in Page_Load() ...