I've always wanted to do this too. The only way I can think of doing that is to use the DrawText API to split up the words between the "invisible" cells since iGrid doesn't currently support combining multiple cells. My guess is that it won't ever unless someone else adds it to the source code we get when we purchase iGrid.
You'd also need to draw your own grid lines and colored boxes around the various cells, if you're wanting it to look exactly like the image, for example.
All of this would be pretty complicated to pull off. I bet the developers of iGrid could create a workaround for you as I described or add it as a feature, but it wouldn't be cheap to add.