function check(field,name){
	for (i=0; i<field.value.length; i++){
		if(field.value.charAt(i)==" "){			
			field.value = field.value.substring(0,i)+field.value.substring(i+1);
			i--;
		}
	}
	if(field.value.length == 0){
		field.focus();
		alert( 'Položka \"' + name +'\"  je povinná' );
		return false;
	}
	for (i=0; i<field.value.length; i++){
            if (((field.value.charAt(i)<"0") || (field.value.charAt(i)>"9")) && (field.value.charAt(i)!=".")){
                alert('Položka \"'+name+'\" může obsahovat pouze číslice a destinou tečku');
                field.focus();
                return false;
            }
	}
  	return true;
}
function calculation(){	
	if(check(document.getElementById('exchangeRate'),"KURZ") && check(document.getElementById('priceCr'),"CENA ZBOŽÍ V KČ")){
		var priceCr = document.getElementById('priceCr').value;
		var exchangeRate = document.getElementById('exchangeRate').value;
		var priceCrEUR = Math.round(priceCr/exchangeRate*100);
		document.getElementById('priceSk').value = priceCrEUR/100;
	}
}