Is it possible to use the change event trigger of an item to get the name of the field?

hi All,

According to this image,

my method name is " change_field ".

The field names of text boxes framed by dashed lines on the screen are "A", "B", "C", and "D".
The text boxes that are framed with dashed lines have a text box below them that is not framed with dashed lines.
The field names are "A1", "B1", "C1", and "D1" respectively.

I want to get the field name of the current trigger method in the method "change_field", and change the value of other text boxes according to the field name.

Example: The user changes the text box with the field name "A" and triggers the method "change_field".
I need to get the field name of the current text box called "A" in the method "change_field" and read the field name of the current text box called "A" to change the value of the field name of the text box called "A1".

But I don't know how to write the syntax of 「get the field name of the current text box as "A"」

If somebody knows and can help I would really appreciate that.

Thank you.