Increment +1 cells with True value - google-sheets

Question

I'm trying to take a set of names with check boxes next to them and make a system so that you can check some of the names (mark them as "True") and click a button. It would then increment +1 the value next to the names of the people marked true.
Here is a link to a sample sheet:
https://docs.google.com/spreadsheets/d/1gf-BrXXR0cAYCn7bMkvvK65R290NXbP9D6aA68c06C8/edit?usp=sharing
If column A, row 2 (Tim's row) is marked true, I want to increment the value in column C, row 2 by one, so Tim would have a running total of tardies next to his name.
I hope this is do-able. Thanks!

Answer 1

(Now I know what you're trying to get)
In order to increment a value via the press of a button, as far as I know you have to use scripts (Tools -> Script Editor). Here's something I threw together:
// editCell takes the cell to edit and it's new value
function editCell(cellName, value) {
SpreadsheetApp.getActiveSheet().getRange(cellName).setValue(value);
}
// getCell takes the cell's value and returns it
function getCell(cellName) {
return SpreadsheetApp.getActiveSheet().getRange(cellName).getValue();
}
// plusOne adds one to the field supplied. It's linked to the button in the sheet
function plusOne() {
editCell("C2",getCell("C2")+1);
}
In order to make it work, you may need to change the targeted Cell (currently C2). You'll also need to create a drawing (Insert -> Drawing) which will act as the button you'll be able to press. Once inserted, click on the three dots on it and click on Link Script. Type in plusOne. When executing it the first time, it'll ask you to authenticate the use of scripts.
That should do the trick. I hope you have some understanding of Java Script though (to modify the code to your needs optimally).
Edit - Expandable version
So, to make every number behind a ticked field increase by one, you can use this version of the code:
// Adds one to every field within "AddArea" that has a tick in front of it. It's linked to the button in the sheet.
function plusOne() {
var ss = SpreadsheetApp.getActiveSheet();
var range = ss.getRange("AddArea");
var values = range.getValues();
var newValues = [];
for (var i = 0; i < range.getNumRows(); ++i) {
var row = values[i];
if(row[0]) {
newValues.push([true, row[1]+1]);
}
else {
newValues.push([false, row[1]]);
}
}
range.setValues(newValues);
}
You need to define a custom named area, named "AddArea" (Data -> Labeled Areas [or similar]), link the script to a button and allow the script to be run. This was hard but very fun to figure out.
Example Sheet for reference (updated)

Answer 2

Can be achieved with just, for example for C2:
=A2+C2
but you would need to turn on iterative calculation (File > Spreadsheet settings... > Calculation [Max. 1 is adequate]) and I would not really recommend that over a trigger with Google Apps Script.