Timestamp for Edits Made to 1 Cell Only

Question

I have this script that works perfectly for any edit on the spreadsheet page:

function onEdit(e) {
   if (!e.value) return;
  e.source.getActiveSheet()
       .getRange('F29')
       .setValue(new Date());
}

However, when I try to modify it so that it only works with edits made to cell C29 (which is actually C29:E29 merged; I don't know if that matters), it won't update when there are edits made to that cell:

function onEdit(e) {
   if (!e.value) return;
  e.source.getCell('CONTENTS','C29:E29')
       .getRange('F29')
       .setValue(new Date());
}

I've tried it with both C29 & C29:E29 for getCell; neither works, so there's obviously something wrong and I'm out of ideas for how to make it work correctly. I'm sure there's an easy answer though...

@Rubén - this is the change I tried:

function onEdit(e) {
   if (!e.value) return;
  e.range.getA1Notation() === 'C29'
       .getRange('F29')
       .setValue(new Date());
}

I also tried this just in case it was an issue with the merged cells:

function onEdit(e) {
   if (!e.value) return;
  e.range.getA1Notation() === 'C29:E29'
       .getRange('F29')
       .setValue(new Date());
}

Sheet link

Answer 1

It's very likely that you are trying to use getCell as it was the same as the CELL built-in spreadsheet function, but it isn't, actually the Class Spreadsheet hasn't a getCell method.

To make a function that only works when C29 is edited use the following condition or something equivalent:

e.range.getA1Notation() === 'C29'

You could use the above as the condition of if...else, switch among other JavaScript control flow statements.