isLoading in UI Policy Script

[Niclas]

In onChange Scripts we can use the isLoading variable to determine if the form has been loaded or is still loading. I tried to use that variable in an UI Policy, but it is undefined there. Is there a similar variable that can be used in UI Policy Scripts? Would it be save to use document.readyState for this purpose? 

[Zmud1]

I tried this solution but it doesn't work. I can't access the document.readyState from UIPolicy script. Can you help me out why that might be?