Button Label change on EVT_BUTTON in wxpython!!!

[Ven]

Some system info before proceeding further:

Platform: Mac OS X 10.7.1
Python Version: ActiveState Python 2.7.1
wxPython Version: [url=http://downloads.sourceforge.net/wxpython/
wxPython2.9-osx-2.9.2.1-cocoa-py2.7.dmg]wxPython2.9-osx-cocoa-py2.7[/
url]

I want the button label to be changed while performing a task

So, here is what I did/want:

self.run_button=wx.Button(self.panel,ID_RUN_BUTTON,label='Install')
self.Bind(wx.EVT_BUTTON, self.OnRun,id=ID_RUN_BUTTON)

def OnRun(self,evt):
	self.run_button.SetLabel('Installing..')
	#call a function that does the installation task
	installation_task()
	#After task completion, set the button label back to "Install"
	self.run_button.SetLabel('Install')

When I try doing this, it doesn't set the label to "Installing" while
the task is being performed. Any suggestions how do I achieve this?