Try this:
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<html>
<head>
<title>Calculator</title>
<%@ Language=VBScript %>
<script language="vbscript">
Dim item1price, item2price, item3price, item4price, witem1, witem2, witem3, witem4, pricetot
item1price = 100
item2price = 100
item3price = 100
item4price = 100
Function count()
If calc.item1.checked Then
witem1 = item1price
else
witem1 = 0
End If
If calc.item2.checked Then
witem2 = item2price
else
witem2 = 0
End If
If calc.item3.checked Then
witem3 = item3price
else
witem3 = 0
End If
If calc.item4.checked Then
witem4 = item4price
else
witem4 = 0
End If
pricetot = witem1+witem2+witem3+witem4
document.calc.pay.value = pricetot
End Function
</script>
</head>
<BODY>
<center>
<form name="calc" method="POST">
<table width="450" border="0" cellpadding="3">
<tr>
<td colspan="2"><span class="normalText"><h4>Checkbox calculator</h4></span></td>
</tr>
<tr>
<th bgcolor="#333333" width="50%" align="left"><span class="whiteText">Item</span></th>
<th bgcolor="#333333" width="50%" align="right"><span class="whiteText">Select</span></th>
</tr>
<tr>
<td bgcolor="#cccccc" colspan="2"><span class="normalText"><b>Item group 1</b></span></td>
</tr>
<tr>
<td bgcolor="#eeeeee"><span class="normalText">Item 1.1</span></td>
<td bgcolor="#eeeeee" align="right"><input type="checkbox" name="item1" size="10"></td>
</tr>
<tr>
<td bgcolor="#eeeeee"><span class="normalText">Item 1.2</span></td>
<td bgcolor="#eeeeee" align="right"><input type="checkbox" name="item2" size="10"></td>
</tr>
<tr>
<td bgcolor="#cccccc" colspan="2"><span class="normalText"><b>Item group 2</b></span></td>
</tr>
<tr>
<td bgcolor="#eeeeee"><span class="normalText">Item 2.1</span></td>
<td bgcolor="#eeeeee" align="right"><input type="checkbox" name="item3" size="10"></td>
</tr>
<tr>
<td bgcolor="#eeeeee"><span class="normalText">Item 2.2</span></td>
<td bgcolor="#eeeeee" align="right"><input type="checkbox" name="item4" size="10"></td>
</tr>
<tr>
<td bgcolor="#cccccc" colspan="2" align="right"><span class="normalText">Price $</span><input type="text" name="pay" size="10" style="background-color:#ffffff; color:#000000; border:1px solid #000000; font-family:tahoma; font-size:8pt; letter-spacing=1px"></td>
</tr>
<tr>
<td bgcolor="#eeeeee" align="center"></td>
<td bgcolor="#eeeeee" align="right"><input type="button" onClick="count()" value="Calculate" style="background-color:#ffffff; color:#000000; border:1px solid #000000; font-family:tahoma; font-size:8pt; letter-spacing=1px"> <input type="reset" value="Reset" style="background-color:#ffffff; color:#000000; border:1px solid #000000; font-family:tahoma; font-size:8pt; letter-spacing=1px"></td>
</tr>
</table>
</form>
</center>
</body>
</html>
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/Matt