'Sql String
Dim strSQL As String = "UPDATE Tab1 SET Aenderung = @Änderung WHERE Aenderung =" & _
  "@Datum "
 
'erstelle Command
Dim com As New OleDbCommand(strSQL, con)
com.Parameters.Add(New OleDbParameter("@Datum", OleDbType.DBDate))
com.Parameters("@Datum").Value = DateTime.Now

VB@rchiv its the Best