Script for subtraction of timestamp

Question

I have a running onEdit script that makes a 2 timestamps on Column B (Date) and C (Time), when something is input in Column A.

My end goal is to make a scrip that, if an Input is done Column A, a subtraction of (Ex: Row 3 - Row 2) in timevalue format in Column D happens , if Column B is the same date, otherwise empty.

I made a formula for this, But I would rather have as script to run everything automatically.

This is the scrip I'm running right now:

function onEdit(e) {

var row = e.range.getRow();
var col = e.range.getColumn();

if(col === 1 && row > 1 && e.source.getActiveSheet().getName() === "Raul") {
  if(e.source.getActiveSheet().getRange(row,2).getValue() == ""){
    e.source.getActiveSheet().getRange(row,2).setValue(new Date());
    if(e.source.getActiveSheet().getRange(row,3).getValue() == ""){
      e.source.getActiveSheet().getRange(row,3).setValue(new Date());   

}
}
}
}

The formula I have currently for Column D is:

=IF(LEFT(B3;10)=Left(B2;10);Timevalue(C3-C2);"")

I would like to have this formula integrated in the script somehow, if possible.