Disabling StepNextButton inside CreateUserWizard control

I want to disable StepNextButton after it's clicked (to avoid multiclicking).
The problem with OnClientClick="this.disabled=true;" that it cancels the postback and doesn't continue to a next wizard step.


<CustomNavigationTemplate>
<table border="0" cellspacing="5" style="width:100%;height:100%;">
<tr align="right">
<td align="right" colspan="0">
<asp:Button ID="StepNextButton" runat="server"
CommandName="MoveNext" OnClientClick="this.disabled=true;"
Text="Create User" ValidationGroup="CreateUserWizard1"/>
</td>
</tr>
</table>
</CustomNavigationTemplate>



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