Don't use ids. Find the second column element relative to the first. For example, if the second column is a text input:
var col1 = jQuery(this);
if(col1.val()==4) col1.closest("tr").find(".InputText").prop("disabled",true);

TomG thanks for the tip, I will try that. What if it's a dropdown list in the second column instead of a text input?

https://www.qualtrics.com/community/discussion/comment/27039#Comment_27039Change find(".InputText") to find("select").

TomG Ok thanks! I got it working somewhat:
jQuery("#"+this.questionId+" input[type='radio']").on('click',function(){
  var col1 = jQuery(this);
  if(col1.val()==4) col1.closest("tr").find("select").prop("disabled",true);
 });
but my issue now is that if I click on N/A and change to one of the other three options, the dropdown list stays disabled. Is there a way I can tweak this further so the dropdown is re-enabled if the selected option is changed?

Add an else to your if to reenable it.

TomG Thank you so much! Think it's working well now:
 jQuery("#"+this.questionId+" inputttype='radio']").on('click',function(){
  var col1 = jQuery(this);
  if(col1.val()==4) col1.closest("tr").find("select").prop("disabled",true);
   else{
       col1.closest("tr ").find("select").prop("disabled",false);
   }
 });

How do I find the "questionID"?

https://community.qualtrics.com/XMcommunity/discussion/comment/53057#Comment_53057You don't need to.

this.questionId

Thank you for sharing this; it works wonders! If I wanted to apply this code to a question where the second column is a radio button (Yes/No), what would I use in place of find("select")?