[shtopor]

<script type="text/javascript"> 
	window.onload = function(){ 
	    var count = 0; 
	    document.getElementById("check").onclick = function(){ 
	        document.getElementById("input").value = (this.checked) ? count+=150 : count-=150; 
	    }; 
	}; 
	</script> 
	  
	<input type="checkbox" id="check" value=""  /> 
           <input type="checkbox" id="check" value=""  />
           <input type="checkbox" id="check" value=""  />
	<input type="text" id="input" value="0" />