Create form wich looks and behaves like Grid

can you post a screenshot what are you trying to do?

and explain what exactly are you struggling with?

I need  to Delete/Insert/Update list Items, depending on clicked action, and refresh this grid. My problem is: how to catch when select is made. I inserted function on validation, but it is fired on load. I need to execute function just when selection is made.

Like last resort I can put button and perform all updates at one shut, but I'd like to do it like Grid, real time. 

Why are not using the Repeating section Control? 

Using the Repeating Section control in Nintex Forms for SharePoint - YouTube 

It is LookUp list, I use it a lot. Repeating Section is not easy to use for this purpose.

to capture dropdown change you can use following code

NWF$('#'+ddl).change(function(evt){
     console.log('dropdown changed to: ' + evt.target.value);
})
‍‍‍

ddl is javascript variable configured for dropdown control.

however, it looks suspicious to me as well what you are trying to do.

single form runtime instance is designed to work on single item, not on several items.

are you trying to mimic list view and its operations within form?

Marian, Thank you very much. It is great. It is working.

that doesn't matter, approach/handler is just the same.

you just have to attach onchange handler to each new dropdown control created at runtime with new repeater rows.

it should be done within NWF.FormFiller.Events.RegisterRepeaterRowAdded event

see event description JavaScript events in Nintex Forms 

and similar example https://community.nintex.com/message/64071-re-evaluating-each-productid-in-a-repeating-section?commentID=64071#comment-6… 

great that it is working.

have you replaced your former question? it might be confusing for someone reading through the thread ...

please mark as correct answer the post that answers original questions so that others experiencing the same problem could from it.

I marked like correct original question. Is it not right?

you should select and mark as correct the post that answers the question. the post is then shown at the top of the page right after the question and everyone who come across this thread can see them both immediately without reading throughout whole long thread.

there are as well several other benefits of marking proper post as correct answer - see  

if you mark as correct some final thankful post it doesn't brings these benefits.