look this:
http://gwt-ext.com/forum/viewtopic.php?f=7&t=2651&hilit=maskin ur html file... put in body
<script language="javascript" src=pathof InputTextMask.js here />
Code:
public class Mask {
public static final String PHONE = "(99)9999-9999";
public static InputMaskPlugin applyMask(String mask,
boolean clearWhenInvalid) {
return new InputMaskPlugin(mascara, clearWhenInvalid);
}
}
Code:
public class InputMaskPlugin extends ComponentPlugin {
public InputMaskPlugin(String mask, boolean clearWhenInvalid) {
jsObj = create(mask, clearWhenInvalid);
}
protected native JavaScriptObject create(String mask,
boolean clearWhenInvalid) /*-{
return new $wnd.Ext.ux.InputTextMask( mask, clearWhenInvalid );
}-*/;
@Override
public void init(Component component) {
}
}
an example!!!
Code:
txtPhone= new TextField();
txtPhone.addPlugin(Mask.applyMask(Mask.PHONE, false));

the plugin can be downloaded here
http://code.google.com/p/cherryonext/