What event are you triggering the action on? I have the following on the Exit event and it works.
if(this.rawValue == "Hide"){
subForm1.presence = "hidden"
}
else
if(this.rawValue == "Show"){
subForm1.presence = "visible"
}
If however you have the "Specify Item Values" button clicked on the Binding tab you will need to change the values from "Hide" to their specified value i.e. "1"

Then you would change the code to:
if(this.rawValue == "2"){
subForm1.presence = "hidden"
}
else
if(this.rawValue == "1"){
subForm1.presence = "visible"
}