Radio Buttons Based on Text Field Value

Below is validation script in the field where the value changes and I have radio buttons with two choices.  When it is greater or equal to 1000, Choice 1 (which is yes).  However, it is not changing to Choice 2 (which is no) when below 1000.

if (event.value >= 1000)
{
   this.getField("CheckBox").valueAsString == "Choice1"
} else {
   this.getField("CheckBox").valueAsString == "Choice2"
}