How to update values from another cell only once, not with subsequent edits?

Question

I have a cell A1, whose values I change periodically.

I have a cell F7:F, I add values to this column from time to time.

I have another cell K7:K whose values depend on what's in A1 and what's in F7:F.

K7=(F7)/(A1*15) --just an example using row 7, K7 would only be filled once there's a value in F7.

However, I only want K7:K's values to change the first time, depending on what's in A1 that time, once I change A1 again, I only want the future values of K7 to change.

What I've tried:

I have a column J7:J, I put in values that I'd be putting in A1, but I'd like to get rid of this cell.

Answer 1

I had to use script editor:

function onEdit(e) {
  var row = e.range.getRow();
  var dateCell = e.range.getSheet().getRange(row, 10);
  if (!dateCell.getValue()) {
    var distance = e.range.getSheet().getRange(row, 6).getValue();
    var A1 = e.range.getSheet().getRange(1, 1).getValue();
    dateCell.setValue(-(distance*A1/(15)));
  }
}