function calc2_step1_check(obj)
{
	correct  = true;

	if(obj.elements['self_income'].value.length < 1)
	{
		alert('Het invoeren van het eigen bruto jaarinkomen is verplicht');
		correct = false;
	}

	return correct;
}

function checkInt(obj)
{
	a = Array ('0','1','2','3','4','5','6','7','8','9');

	var oldvalue = obj.value;
	var newvalue = '';

	for(i=0;i<oldvalue.length;i++)
	{
		for(j=0;j<a.length;j++)
		{
			if(oldvalue.substring(i,i+1) == a[j])
				newvalue = newvalue + oldvalue.substring(i,i+1);
		}
	}
	obj.value = newvalue;
}

function chg_child(obj)
{
	if(obj.checked)
		document.getElementById('tab_'+obj.name).style.display = '';
	else
		document.getElementById('tab_'+obj.name).style.display = 'none';
}