Hi,
By default the composed text style is the text style of the drawing document and every change changes it directly. That is why the style of the last shape is applied to the document's text style and then to all other shapes.
To avoid this issue, you should clone the composed text style and then modify the cloned version. Here's how to clone it:
Dim textStyle As NTextStyle = CType(s.ComposeTextStyle().Clone(), NTextStyle)
To save memory and improve performance we recommend you clone and apply a text style only to shapes whose text style should be different from the text style of the drawing document.
Best Regards,
Nevron Support Team