I don't know if this helps, but i found this on a website, maybe someone can convert it into plus scripting?
code:
<script language="JavaScript">
var m;
m = 0;
var i;
var mm;
function num ( i ) //delete the spaces here
{
var u = new String();
u = text3.value;
if (u == "=")
{
text1.value = text2.value = "";
text1.value = text1.value + i ;
text3.value = "";
return;
}
var s;
var l;
s = text1.value;
l = s.length;
if (l<10)
{
text1.value = text1.value + i;
}
}
function point()
{
var i;
var s = new String();
s = text1.value;
i = s.indexOf(".");
var u = new String();
u = text3.value;
if (u == "=")
{
text1.value = text2.value = "";
text1.value = text1.value + "." ;
text3.value = "";
return;
}
if (i > -1)
{
return;
}
else
{
if (s.length<9)
{
s = s + ".";
text1.value = s;
}
}
}
var cho;
function act(cho)
{
var u = new String();
u = text3.value;
if (u == "")
{
text2.value = text1.value;
text1.value = "";
}
else
{
switch 
{
case "+" :
text2.value = (text2.value*1) + (text1.value*1);
text1.value = "";
break;
case "-" :
text2.value = (text2.value*1) - (text1.value*1);
text1.value = "";
break;
case "*" :
text2.value = (text2.value*1) * (text1.value*1);
text1.value = "";
break;
case "/" :
text2.value = (text2.value*1)/(text1.value*1);
text1.value = "";
break;
case "=" :
text2.value = text1.value;
text1.value = "";
break;
}
}
switch (cho)
{
case 1 :
text3.value = "+";
break;
case 2 :
text3.value = "-";
break;
case 3 :
text3.value = "*";
break;
case 4 :
text3.value = "/";
break;
}
}
function eq()
{
switch (text3.value)
{
case "+":
text2.value = (text2.value*1) + (text1.value*1);
text1.value = text2.value;
text2.value = "";
break;
case "-":
text2.value = (text2.value*1) - (text1.value*1);
text1.value = text2.value;
text2.value = "";
break;
case "*":
text2.value = (text2.value*1) * (text1.value*1);
text1.value = text2.value;
text2.value = "";
break;
case "/":
text2.value = (text2.value*1) / (text1.value*1);
text1.value = text2.value;
text2.value = "";
break;
}
text3.value = "=";
}
function clss()
{
text1.value = text2.value = text3.value = "";
m =0;
clear1.blur();
}
function initia()
{
text1.blur();
text2.blur();
}
function clearall()
{
text1.value = "";
}
function madd()
{
m = m + ((text1.value)*1);
text1.value = "";
text3.value = "";
}
function msub()
{
m = m - ((text1.value)*1);
text1.value = "";
text3.value = "";
}
function mrem()
{
if (m != 0)
{
text1.value = m;
text3.value = "";
}
}
function free()
{
if (mm != 1)
{
alert ('JavaScript disables this action!!');
}
}
function frees()
{
mm = 1;
}
function freed()
{
mm = 0;
}
</script>
/ 
