I want to change mask and format edit on client side using javascript.

Before action I have webinput. e.g.

<ISWebInput:WebInput ID="WebInput4" runat="server" Width="140px">
	<EditFormat>						                            
		<ErrorWindowInfo IsEnabled="True">
		</ErrorWindowInfo>
	</EditFormat>					                            
</ISWebInput:WebInput>

 I am trying to obtain on client side somthing similar to:

<ISWebInput:WebInput ID="WebInput4" runat="server" Width="140px">
	<EditFormat Format="00-000" IsEnabled="True" Type="Other">
		<MaskInfo MaskExpression="00-000">
		</MaskInfo>
		<ErrorWindowInfo IsEnabled="True">
		</ErrorWindowInfo>
	</EditFormat>
	<HighLight IsEnabled="True" />
</ISWebInput:WebInput>

 I wrote some code in javascript to do this: 

var oWebInput = ISGetObject('WebInput4');
oWebInput.EditFormat.Format = '00-000';
oWebInput.EditFormat.Enabled = true;
oWebInput.EditFormat.MaskType = 'Other';
oWebInput.EditFormat.MaskInfo.MaskExpression = '00-000';

Unfortunately  it does not work .New mask is not appear. 

Please.Could you suggest me some solution of my problem using javascript.

Regards,

Mariusz