Check if is possible to click on a button or not in an IFrame

I have application with an IFrame which popups dynamically. I handle that with a Frame "framenavigated". The challenge is that frame has two different modes depending on a schedule. In one mode you need to click on a button to open the frame and access the other elements. In the other mode it is open automatically. The button can not be accessed with a click. You will also have different elements in the frame depended on the mode. I can not use Locators directly due to the will cause a failure when I try to work with locator which not exist. Or in case of the button, I want test if it is clickable without causing a failure. I think I need to access the DOM directly with evaluate() or evaluateAll(). Thankful for any kind of help here.