Thanks for the feedback. The problem with the explicit sizes is that the application has no way of knowing what is a reasonable limit, AFAIK. Since oocalc doesn't crash, I guess it has some logic that copes; maybe I'll take a look at the code. One thought that occurs to me is that it should be possible to write a function that starts from a cell and works back and up through the tree to calculate the position of that cell. I may try writing that. With some cacheing of results, it might even be reasonably efficient.