A family of Microsoft relational database management systems designed for ease of use.
I was able to change the text in the cell by selecting the shape and then selecting the cell. Another way to do it is to have nothing selected and chose the Text Tool (the letter A) and click on the shape. Click on the shape over the text you want to change. This should open a text window so you can change the text.
John... the original Visio MVP (since 1993) Visio.MVPs.org