How to use Google app script to automatically border line below When Value Changes - google-sheets

Question

I want to add a border line below the row whenever column C value changes.
I haven’t touched macro for a long time, this is a script I put together but it doesn’t work as expected. Anyone know where the problem is? Thanks!
function underline() {
var spreadsheet = SpreadsheetApp.getActive();
var sheet = spreadsheet.getActiveSheet();
for (var i = 1; i < 10; i++) {
if (sheet.getRange(spreadsheet.getCurrentCell().getRow() + i, 3) != sheet.getRange(spreadsheet.getCurrentCell().getRow() + i+1, 3)) {
sheet.getRange(spreadsheet.getCurrentCell().getRow() + i, 1, 1, sheet.getMaxColumns()).activate();
spreadsheet.getActiveRangeList().setBorder(null, null, true, null, null, null, '#000000', SpreadsheetApp.BorderStyle.SOLID);
}
}
};

Answer 1

Your original code is a bit convoluted, doing a lot with a single if statement. I took the liberty to separate the complicated bit into a distinct function, findOriginal(cell). The following code adds one line:
function findOriginal(cell) { //offsets given cell until finds new content
while (cell.getValue() == cell.offset(1,0).getValue()) cell = cell.offset(1,0);
return cell;
}
function underline() {
var spreadsheet = SpreadsheetApp.getActive(),
cell = spreadsheet.getSelection().getCurrentCell();
cell = findOriginal(cell);
var sheet = spreadsheet.getActiveSheet();
sheet.getRange(cell.getRow(), 1, 1, sheet.getLastColumn()) // setting the range to border
.setBorder(null, null, true, null, null, null,
'#000000', SpreadsheetApp.BorderStyle.SOLID); // you wrote this line
};