Código HTML:
<script> function restar(forma){ var minuendo=document.getElementsByName(forma)[0].minuendo.value; var sustraendo=document.getElementsByName(forma)[0].sustraendo.value; var diferencia=minuendo - sustraendo; document.getElementsByName(forma)[0].minuendo.value=diferencia; /* Opcionalmente borramos el campo del 'sustraendo' */ document.getElementsByName(forma)[0].sustraendo.value=""; } </script> <? echo "<FORM METHOD='POST' ACTION='Provisionar1.php' name='resta'>"; echo "<table width='100%' border='1' align='center' cellpadding='2' cellspacing='2' bgcolor='#000099'>\n"; echo "<tr> \n"; echo "<td align='center'><font color='#00FF33' face='Maiandra GD'><b>Contratista</b></font></td> \n"; echo "<td align='center'><font color='#00FF33' face='Maiandra GD'><b>% Asignación * Calificación</b></td> \n"; echo "<td align='center'><font color='#00FF33' face='Maiandra GD'><b>Cuadrillas</b></td> \n"; echo "<td align='center'><font color='#00FF33' face='Maiandra GD'><b>% Capacidad</b></td> \n"; echo "<td align='center'><font color='#00FF33' face='Maiandra GD'><b>% Asignación Total</b></td> \n"; echo "<td align='center'><font color='#00FF33' face='Maiandra GD'><b>Cupo Sugerido</b></td> \n"; echo "<td align='center'><font color='#00FF33' face='Maiandra GD'><b>Cupo Asignado</b></td> \n"; echo "<td align='center'><font color='#00FF33' face='Maiandra GD'><b>Observación</b></td> \n"; echo "</tr>"; $sSQL="SELECT * FROM nota_contratista "; $result=mysql_query($sSQL); $s=0; while ($row=@mysql_fetch_array($result)) { $sugerido=$row[10]; echo "<tr> \n"; echo "<input type='hidden' name='numero[]' value=".$row[0].">"; echo "<td align='center'><font color='#999999' face='Maiandra GD'><b>".$row[1]."</b></font></td> \n"; echo "<td align='center'><b>".$row[6]."</b></td> \n"; echo "<td align='center'><b>".$row[7]."</b></td> \n"; echo "<td align='center'><b>".$row[8]."</b></td> \n"; echo "<td align='center'><b>".$row[9]."</b></td> \n"; echo "<td align='center'><b>$sugerido</b></td> \n"; ?> <td align="center"><input type="text" name="sustraendo" onBlur="restar('resta');"></td> <? echo "<td align='center'><textarea name='observacion[]' cols='30' rows='2'></textarea></td> \n"; echo "</tr>"; $s=$s+$sugerido; } echo "</table>"; echo "<table width='47%' border='1' align='right' cellpadding='2' cellspacing='2' bgcolor='#000099'>\n"; echo "<tr>"; echo "<td width='19%' align='center'><font color='#00FF33' face='Maiandra GD'>Total: </font></td>"; ?> <td width="81%"><input type="text" name="minuendo" value=<? echo $s?> ReadOnly></td> <? echo "</tr>"; echo "</table><br><br>"; echo "<INPUT TYPE='SUBMIT' value='Aceptar'></td>"; echo "</form>";