Checkbox and recalculate

I have a sheet where two numbers A and B are randomly generated - lets say C is calculated from A x B = C. The cell containing the answer C contains an IF statement such that the answer is only shown if a checkbox (Show Answers) controlling a cell allows it. I want to reveal the answer by checking the checkbox (Show Answers). Unfortunately it sets the controlled cell to TRUE and initiates a recalculate, causing new randowm numbers A and B to be calculated and the new answer to A x B = C to be shown. How do I arrange it so that the original answer is revealed? (i.e. the answer to the orignal A x B = C before the checkbox kicked off the recalculate?)

regards
Neil

PS What is the difference between the checkbox from the forms toolbar and from the Controls Toolbox? I always use the one from the forms toolbar - how best should I understand the different purposes of each checkbox control?

Bump - anyone have any useful ideas about this? Is it possible to programmatically enable/disable (e.g. an IF statement) recalculate for certain cells? Maybe a totally different approach is needed.

regards
Neil