validation summary must be visible only on save button click and not on any other button

i have few controls which r validated for blank on a page having 5 buttons

i want the validation to take place only on save button click & not on any other button

 <asp:ValidationSummary ID="ValidationSummary1" HeaderText="You must enter a value in the following fields:"
                                                                            EnableClientScript="true" ShowMessageBox="true" ShowSummary="false" DisplayMode="BulletList"
                                                                             runat="server" />