warning message not working

[Aneeshmohan]

I want to show a warning message in user interface side in my module in a particular condition.For that I have write the code like this.

    raise osv.except_osv(('Warning!'), ("Entered Quantity is greater than quantity on source."))

But in that condition in user interface side it just showing the loading image.

At the console I got the error like this.

> 2013-06-10 09:45:53,612 364
> ←[1;31m←[1;49mERROR←[0m None
> openerp.netsvc: Warning! Entered
> Quantity is greater than quantity on
> source. Traceback (most recent call
> last): File
> "C:\OpenErp\openerp\openobject-server\openerp\netsvc.py",
> line 361, in dispatch_rpc
> result = ExportService.getService(service_name).dispatch(method,
> params) File
> "C:\OpenErp\openerp\openobject-server\openerp\service\web_services.py",
> line 585, in dispatch
> res = fn(db, uid, *params) File "C:\OpenErp\openerp\openobject-server\openerp\osv\osv.py",
> line 167, in execute_kw
> return self.execute(db, uid, obj, method, *args, **kw or {}) File
> "C:\OpenErp\openerp\openobject-server\openerp\osv\osv.py",
> line 121, in wrapper
> return f(self, dbname, *args, **kwargs) File "C:\OpenErp\openerp\openobject-server\openerp\osv\osv.py",
> line 176, in execute
> res = self.execute_cr(cr, uid, obj, method, *args, **kw) File
> "C:\OpenErp\openerp\openobject-server\openerp\osv\osv.py",
> line 164, in execute_cr
> return getattr(object, method)(cr, uid, *args, **kw) File
> "C:\OpenErp\openerp\openobject-addons\mat_mgmt\mat_mgmt.py",
> line 101, in button_confirm
> raise osv.except_osv(('Warning!'), ("Entered Quantity is greater than
> quantity on source.")) except_osv:
> ('Warning!', 'Entered Quantity is
> greater than quantity on source.')
> > c:\openerp\openerp\openobject-addons\mat_mgmt\mat_mgmt.py(101)button_confirm()
> -> raise osv.except_osv(('Warning!'), ("Entered Quantity is greater than
> quantity on source."))

I want to show the warning message on user interface side.