[null]

<form method='POST' name='register' onsubmit='return Validate()'>
<input type='checkbox' name='a' value='1'>
<input type='checkbox' name='a' value='2'>
<input type='checkbox' name='a' value='3'>
</form>

[eLad]

משהו כזה?

document.frmName.checkBoxName.value==1