Validar textbox

[eduardo1983]

<script language="javascript">

var downStrokeField;



function autojump(fieldName,nextFieldName,fakeMaxLength)
{

var myForm=document.forms[document.forms.length - 1];

var myField=myForm.elements[fieldName];

myField.nextField=myForm.elements[nextFieldName];

if (myField.maxLength == null)

myField.maxLength=fakeMaxLength;

myField.onkeydown=autojump_keyDown;

myField.onkeyup=autojump_keyUp;
}



function autojump_keyDown()

{

this.beforeLength=this.value.length;

downStrokeField=this;

}



function autojump_keyUp()

{

if ((this == downStrokeField) && (this.value.length > this.beforeLength) && (this.value.length >= this.maxLength))

this.nextField.focus();
downStrokeField=null;

}

</script>

<form>
<input type=text name="contador1" size="2" maxlength="2">
<input type=text name="contador2" size="2" maxlength="2">
<input type=text name="contador3" size="2" maxlength="2">
<input type=text name="contador4" size="2" maxlength="2">

</form>

<SCRIPT TYPE="text/javascript">
//PARA EL NÚMERO DE CHEQUE
autojump('contador1', 'contador2', 2);
autojump('contador2', 'contador3', 2);
autojump('contador3', 'contador4', 2);


</SCRIPT>