Waiting for Button to be enabled

Hello.  I am new to TestComplete and would like to ask if someone can help.

I need to wait for this button to becomes enable so I can move on, the enabled time varies on the button but no longer than 30 seconds. I prefer not to use the Delay command because the script will take too long to complete.

I am trying to use the following script in my keyword but it is giving me a code error within the script. "TypeError::WaitProperty is not a function. "  It must be something silly but because I am new to this I do not know where to start.

function WaitForButton() {   

var button = Aliases.browser.pageExam.buttonOn.Enabled

          if (button.WaitProperty("Enabled", true, 35000))

{

           button.ClickButton();

}
}