[V8i C++] Approach To Edit A Cell's Text Node Inside OnElementModify()

In my MStnElementSetTool, I want to be able to edit the contents of a text node. Once in OnElementModify() I have the cell, and I can use a ChildElemIter to find the Text Node that I want to "edit". Once I have the Nodes' ElementRef, what's the best way to alter the node's text content. One requirement is that I need the TextNode number to remain the same. I'm not sure I've ever programatically "edited" a Text Node before. How does one achieve this? Is there a way to remove the existing text elements and "add" the new one(s) to the TextNode?

Thanks,

Bruce