Thanks everyone for their input. I finally have it working and here is the code that works.
What this code does is when a change event is triggered in a drop down (this)that meets the either or condition it makes a subform (DischargedToForm)containing a text box visible for additional information input.
if (this.rawValue=="SNF" || this.rawValue=="Custodial")
DischargedToForm.presence = "visible";
else
DischargedToForm.presence = "hidden";
Your script work for all the values of the items to the if item, making it visible. Try your script first in your designer first. It does not work for me with Acrobat 8.1.2.
"_DischargeToForm" means "DischargeToForm.instanceManager".
"invisible" makes form invisible but have place on the form.
"hidden" makes form invisible and remove from layout also.