Radio Button choice displays answer in text field box
I am trying to do a simple task, but keep running into a brick wall. I need my client to select 1 radio choice out of 3 buttons, and have whatever choice the tic, display in a text boxt at the end of the road, automatically. My radio group is called Payment Date. The 3 choices are: 1st/month, 3rd/month, 10th/month. That is the actual name of my three options too. Whichever chosen needs to appear in the text box as the same wording. I have tried several calcualtion scripts but it only shows the first option. I don't know how to add the other two, so they will show when chosen. Last script attempted below. See pics for details.

var showField = (this.getField("Paymentdate").valueAsString=="Yes")
if (showField) event.target.display = display.visible;
else {event.target.display = display.hidden; event.value = "1st/month";}
