vba to make visible 1 or 2 or both worksheets depending if 1 or 2 or both cells selected

I have a workbook with 6 sheets. First sheet has 2 cells, which if I put a check in A1, this is also reflected in sheets2, 3 and 4. Same with cell A2. If I select A1 on ANY of the four sheets, then I want sheet5 to be visible and remain visible until none of the A1 cells are checked. This I have figured out by using an "IF" statement off to the side, giving each cell a value of 1 for each sheet and then in the macro, if the sum of the "IF's" is >= to 1, then sheet5 remains visible. Now the problem. Now I have A2, which if I put a checkmark in it, then I want sheet6 to be visible, which is fine, I can do the same with it as sheet5. But how do I tie the two together, so that if any A1 on sheets1-4 and A2 on sheet1 is checked, then both sheet5 and sheet6 are visible? Of course when A2 on sheet1 and all of the A1's are not checked, both sheets must not be visible, but I can figure that out from the one macro, just reverse it. Any ideas how to make this happen?? Thanks for the help folks!