How can I retrieve the displayed value of a field like `KNA1-LIFNR`, or in cases like `DFKKBPTAXNUM`

I request to fetch the worth that is presently shown connected the surface (in the form) for a azygous field, specified arsenic `KNA1-LIFNR`, oregon aggregate values from a tract similar `DFKKBPTAXNUM`, alternatively than the worth stored successful the database. This is for validation purposes wrong an SAP method. What is the champion mode to get these displayed values?