Hello People.
Do you know what is wrong with this expression? I am trying to add a row update event.
What widget are you working with and where are you trying to enter that? If you’re doing the row-update widget, you need to put that in the expression field, not the value. The value field is expecting JSON syntax as that error describes.
You’re also trying to divide a string instead of a numerical field. Take the quotes off when you put that in the expression field.
Hey Thanks Willet for the prompt reply. I am trying this very first time. 
I am going to follow the same.
Also, can you please let me know how I call something like tool_event which we are doing in classic customizations?
okay thanks. I will try that.
Last question for today and also enough for me to learn further.
c# code has code in after_RowChange(I think here I need to user after row change event) but in the event it is taking value from current dataset and calling a sales order adapter.
Like this:How I can implement this in Application studio?
and calling adapter with method? via Rest calling
Spot on.
thanks Willett. It made my day. I got enough information to learn and grow. Will come back with more queries.
Got one question: How I can disable a few columns in my custom events? The reason why I need here because I have condition getting values from Rest calling.