Add multiple text to activity

[bodo_koerner]

When I create a text for an activity, the first text is accepted.
When I try to add another text I receive an error "DATREF_NOT_ASSIGNED".
How can I add multiple text types to the same acticvity

// Create a text of type "Body Text" s. DataTypes in RepExplorer

10002 = Body Text instActivityTxtColl = instActivity.TextCollection.Create();
elActivityTxtCollTxt.TypeCode.content = "10002";
instActivityTxtCollTxt = instActivityTxtColl.Text.Create(elActivityTxtCollTxt);
elActivityTxtCollTxtCntnt.Text.content = "10002 Body Text from InfoText:" + "\n" + this.Infotext; instActivityTxtCollTxt.TextContent.Create(elActivityTxtCollTxtCntnt);

// Add other text ? Error: DATREF_NOT_ASSIGNED ?
if (instActivityTxtColl.IsSet())
{
elActivityTxtCollTxt.Clear();
elActivityTxtCollTxt.TypeCode.content = "10023";
instActivityTxtCollTxt = instActivityTxtColl.Text.Create(elActivityTxtCollTxt);
elActivityTxtCollTxtCntnt.Clear();
elActivityTxtCollTxtCntnt.Text.content = "10023 Service Details:"; instActivityTxtCollTxt.TextContent.Create(elActivityTxtCollTxtCntnt);
}