Just had a look at the docs and it seemed like something was missing so i tried it out with the SceneGraphXMLTutorial code.
Markupgrid is different from, say, RowList in that it doesn't map 2D data and give 2D indices into that data. Rather, it takes a linear list of data and it just lays out that linear list on screen by wrapping based on the value of numColumns.
So your row and column would be
rowFocused = itemFocused \ numColumns
columnFocused = itemFocused MOD numColumns
If you use the sections dividers, i don't have an answer there. You'd have to account for empty places in the grid as you encountered each section divider. In that case I would personally use a different component such as RowList.
