Removendo a Linha Desejada

Bom dia galera !

Estou com o seguinte problema:

Tenho um código ao qual quero deletar uma linha qualquer da minha tabela.

O problema é que não estou conseguindo deletar a linha corrente, somente consigo deletar a última linha !

Já tentei passar o valor do botão por this, por perenteElement, parentNode e nada..

Alguém poderia me ajudar ?

Abaixo segue o código

Javascript

<script language="JAVASCRIPT">
function addRowToTable()

{

 var tbl = document.getElementById('tblSample');
 var lastRow = tbl.rows.length;
 // if there's no header row in the table, then iteration = lastRow + 1
 var iteration = lastRow;
 var row = tbl.insertRow(lastRow);

 // left cell

 // right cell
 var cellRight = row.insertCell(0);
 var el1 = document.createElement('input');
 el1.type = 'text';
 el1.name = 'txtRow' + iteration;
 el1.id = 'txtRow' + iteration;
 el1.size = 10;

 cellRight.appendChild(el1);

 var cellRight = row.insertCell(1);
 var el1 = document.createElement('input');
 el1.type = 'text';
 el1.name = 'txtRow' + iteration;
 el1.id = 'txtRow' + iteration;
 el1.size = 10;

 cellRight.appendChild(el1);

 var cellRight = row.insertCell(2);
 var el2 = document.createElement('input');
 el2.type = 'text';
 el2.name = 'txtRow' + iteration;
 el2.id = 'txtRow' + iteration;
 el2.size = 10;

 cellRight.appendChild(el2);

 var cellRight = row.insertCell(3);
 var el3 = document.createElement('input');
 el3.type = 'text';
 el3.name = 'txtRow' + iteration;
 el3.id = 'txtRow' + iteration;
 el3.size = 10;

 cellRight.appendChild(el3);

 var cellRight = row.insertCell(4);
 var el4 = document.createElement('input');
 el4.type = 'button';
 el4.name = 'btn' + iteration;
 el4.id = 'btn' + iteration;
 el4.value = 'Excluir';

 el4.onclick = removeRowFromTable;
 cellRight.appendChild(el4);

}
function removeRowFromTable()

{

 var tbl = document.getElementById('tblSample');
 var lastRow = tbl.rows.length;
 if (lastRow > 2) tbl.deleteRow(lastRow - 1);
}
function openInNewWindow(frm)

{ // open a blank window

 var aWindow = window.open('', 'TableAddRowNewWindow',
 'scrollbars=yes,menubar=yes,resizable=yes,toolbar=no,width=400,height=400');

 // set the target to the blank window
 frm.target = 'TableAddRowNewWindow';

 // submit
 frm.submit();
}
function validateRow(frm)

{

 var chkb = document.getElementById('chkValidate');
 if (chkb.checked) {
	var tbl = document.getElementById('tblSample');
	var lastRow = tbl.rows.length - 1;
	var i;
	for (i=1; i<=lastRow; i++) {
 var aRow = document.getElementById('txtRow' + i);
 if (aRow.value.length <= 0) {
 alert('Row ' + i + ' is empty');
 return;
 }
	}
 }
 openInNewWindow(frm);
}
</script>

HTML

<form action="tableaddrow_nw.html" method="get">
<span id="spanOutput" style="border: 1px solid #000; padding: 3px;"> </span>
</p>
<table border="1" id="tblSample">
 <tr>
	<th>NF</th>
	<th>Peso</th>
	<th>Valor Estimado</th>
	<th>Volume</th>
 </tr>
 <tr>
	<td><input type="text" name="txtRow1" id="txtRow1" size="10"/></td>
	<td><input type="text" name="txtRow2" id="txtRow2" size="10"/></td>
	<td><input type="text" name="txtRow3" id="txtRow3" size="10"/></td>
	<td><input type="text" name="txtRow4" id="txtRow4" size="10"/></td>
	<td><input type="button" value="Add" onclick="addRowToTable();" />
 <input type="button" value="Remove" onclick="removeRowFromTable();" />
 <input type="button" value="Submit" onclick="validateRow(this.form);" />
 <input type="checkbox" id="chkValidate" /> Validate Submit</td>

 </tr>
</table>
</form>