Show a button based on which layers are visible (javascript)

So I've got a "Game" I've made in Acrobat where the user clicks on certain buttons and a layer appears. I wanted to do a final "congratulations" thing at the end when they click on the finish button.

Basically If "Layer 20" and "Layer 11" (and some others that I haven't done yet) are visible and the rest are not then I want the button "Complete" to appear.

Otherwise I'd like it to reset the visibility of the layers to the default state.

This is as far as I've got:

function FindOCG(cName) { 
    var aOCGs = this.getOCGs(); 
    for(var i=0; aOCGs && i<aOCGs.length;i++) { 
        if(aOCGs[i].name == cName) return aOCGs[i]; 
    } 
    return null; 
}
if(FindOCG("Layer 20"&&"Layer 11").state=true) 
{
this.getField("Complete").display=display.visible;
}
Else
{
this.getField("Complete").display=display.hidden;
}

If 20 and 11 are visible it appears okay, but if they're not visible and I click the Finish button then those layers appear and so does the finish button.

Please can anyone help, I'm so stuck now.