You can add custom javascript to your page, but this isn’t terribly common as those activities would be processed on the browser side.

Most events in Acumatica are handled at the server rather than the browser.  The Acumatica way of defining an “on blur” type event is achieved in via 2 steps.  Set the field to Commit Changes = true on the screen definintion (aspx) to enable a postback when focus leaves the field (i.e., onblur).  You then perform your logic in the FieldVerifying, FieldUpdating, or FieldUpdated events in C#.  Alternatively, you might perform your logic on the row level events.

I’d suggest digging into the Developer training material on openuni.acumatica.com.  The Acumatica help also contains details about Event Handlers.

Hi @brianstevens thanks for replay! oke i will try it, thanks for your suggest