Sorry - think I misunderstood what you wanted to do
try a different approach.
1. link to your spreadsheet (can use transferspreadsheet for this or do it through the external data tab) - call it the same name as your worksheet for simplicity in the examples below. Once linked, if you subsequently make changes in the spreadsheet they will be reflected in the linked table so this is a one time exercise
2. create an update query to update existing records - something like
Code:
UPDATE ProjektDelledning INNER JOIN Concatenate ON ProjektDelledning.DelledningID= Concatenate.DelledningID
SET ProjektDelledning.SaneringsmetKode = Concatenate.SaneringsmetKode
3. create an append query to add new records - something like
Code:
INSERT INTO ProjektDelledning (DelledningID, SaneringsmetKode)
SELECT Concatenate.DelledningID, Concatenate.SaneringsmetKode
FROM ProjektDelledning LEFT JOIN Concatenate ON ProjektDelledning.DelledningID= Concatenate.DelledningID
WHERE Concatenate.DelledningID Is Null