Footnotes depend from dropdown value

Hi there, 

I am creating complex document, where the amount of pages depedns from user. Also there is a lot of footnotes in it (placed in Master Pages). Some of them, which should appear when the normal text fild is visible, I made as exaple below (written at layout:ready on footnote subform).

But I also have some footonotes which depend from dropdown list, f.ex. only when value = 3 it shows, else hidden. Please kindly advise. 

if(xfa.layout.page(this) == xfa.layout.page (textfield)){

this.presence ="visible";

}

else {

this.presence ="hidden";

}