Hello Frisher,
For the input field, define an action for the following event:
onEnter.
So this method gets called when the user clicks enter button by placing the cursor in the input field.
However, there is no event available in WD ABAP when the user leaves the field. In WD Java(latest version) has onCHange event which is called when the user leaves the field.
So, you have to manage with the event onEnter which is called when user clicks Enter button with cursor in the field.
Regards,
Sharath