Update button enabled/disabled

[pancakesplatter]

I need help with my update button. I need it so when you start the application the form itself will check for updates and if there is no update the update button will be disabled. If there is a update then the button will be enabled and you can click it and update the program to the latest version. Here are screenshots of what i mean by enabled/disabled:
Enabled:

Disabled:

[Hack]

Forget the buttons for a second....if there is an update how does the machine know it?

[jmcilhinney]

What's the point of a Check For Updates button if it is disabled? Surely the point of a Check For Updates button would be to check whether there is an update or not. If the app has already checked for updates and knows whether there is one or not then the button is not for checking for updates but for installing a known update, so that text is misleading.