Set ItemCode on Order

Hi,

I am working in the sales order form (type 139).

I try to fill the order screen by code (with UI).

So I try to set a value in the ItemCode field per setting the string property of the columns-cell-specific.

itemcode = <some existing itemcode (i check on existance)>
Idx = 1
oEdit = oMArtikel.Columns.Item("1").Cells.Item(Idx).Specific
oEdit.String = itemcode

On the last line an error occur:

System.Runtime.InteropServices.COMException - Form - Invalid Form Item

Is this a restricted action or am I doing something wrong?

Greetz

Eddy