[Connect C++ MicrostationApi] Problem with changing textelement in cell

Hello,

I am trying to change the Text of a  cell with the Microstation C++ Api. 

The Code I am using is working well on normal Text Elements. But in a Cell the "ReplaceInModel" returns an Error (69645)

void TextTool::textChange(EditElementHandleP eehIn)
{
	int result=0;
	switch (eehIn->GetElementType())
	{
	case CELL_HEADER_ELM:
	{				
		for (ChildEditElemIter eehChild(*eehIn); eehChild.IsValid(); eehChild=eehChild.ToNext())
		{
			textChangeTest(&eehChild);
		}
		break;
	}
	case TEXT_ELM:
	{
		TextBlockPtr textBlock = TextHandlerBase::GetFirstTextPartValue(*eehIn);
		ITextEditP textEdit = eehIn->GetITextEdit();          
		// Extract the TextBlock from the Text element.
		if (!textBlock.IsNull() && !textBlock->IsEmpty())
		{
			//Replace Text
			CaretPtr startCaret = textBlock->CreateStartCaret();
			CaretPtr endCaret = textBlock->CreateEndCaret();
			textBlock->ReplaceText(L"newText", *textBlock->CreateStartCaret(), *textBlock->CreateEndCaret());
			//create new Element and replace in Model
			EditElementHandle newEeh;
			ElementHandle templateEh(eehIn->GetElementP(), ACTIVEMODEL);
			TextHandlerBase::CreateElement(newEeh, &templateEh, *textBlock);
			//Replace in model. Working on single textelements but not in cells...?
			result =newEeh.ReplaceInModel(eehIn->GetElementRef());
			wprintf(L"Result replaceInModel: %d\n", result);
		}
		break;
	}
	}

}

Can somebody help me?

Regards

Manuel Höger