changes of AP invoices

Dear gurus,

I'm facing following challenge:

For AP invoices/credit memos (document type KR, KG, RE) we would like to track reasons for changing.

I.e. if user change text field, or any other changeable field on document line item level he/she must enter reason code for that action. These reason codes should be available to pick from drop-down list and for our AP invoices/credit memos it should be mandatory. Based on reason codes, we can report most frequently reasons for modification of invoices/credit memos.

Is there some easier way as adding new field in bseg and make completely new z development?

thanks in advance for inputs.