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We would need more details (maybe even attach a .zip sample of your workbook) so that we can help you here.

You could use conditional formatting to change the font color to white. That's not completely hidden, but it won't jump out at a glance.

Actually, you're right - I can use the conditonal formatting - just use the "Formula is" =NOT(cell reference for flag set by checkbox). This still forces a recalculate though as my numbers are generated using =randbetween(0, N) - is there a way to prevent certain cells from updating? I know that I can go to Tools..Options..Calculation...and set Manual - (never tried that though) but is there a way to set the manual or automatic mode by calls made from a macro that is kicked off by the checkbox change?

is there a way to set the manual or automatic mode by calls made from a macro that is kicked off by the checkbox change?

Yes, but how depends on the type of checkbox (Forms vs Control Toolbox).

Application.Calculation = xlCalculationManual
Application.Calculation = xlCalculationAutomatic