I want to format cells so when you click in them, an X (really, just two lines from corner to corner) appears and the box registers that it is not empty so I can detect this state. (You can tell I’m new at this, right?)

All the advice I’ve seen is about checkbox forms that sit on top of the spreadsheet, but I want the cell itself to check or uncheck. I swear I’ve seen this done…and I hope it’s easy. Anyone?

Then, once I’ve done that, perhaps someone can tell me what controls to use to “count” the number of checked cells among a set of cells. (This is for tallying results of a yes/no survey, by the way.) Am I out of my depth or can this be done by a generally intelligent person?