reset cells button and creating a pop up box

hi, i have created a sheet to make life easier at work. some other branches want a copy, but they often take credit for my stuff. i want to create a box that pops up on opening that says something like 'i agree to pass on all credit to jamie pullen and not take credit for my own'

with a yes and no box. if they cick no, the sheet closes, if yes, they can access the sheet.

also, there ae three sets of cells i would like to be able to reset independantly with three reset butons.

cells B3:I3 with a reset box in cell C20 called 'Clear Rx'

Cells A10:P10 with a reset box in I20 called 'Clear Pair 'A' '

Cells A18:P18 with a reset box in P20 called 'Clear pair 'B' '

I do not know where to start with the pop up box, but can just about create buttons in the required cells that do not do anything, so any help with the code would be amazing!

Thanks in advance,

jamie

as always, thanks alot!