<SCRIPT LANGUAGE=vbscript>
<!--
sub add_a_onclick
frm.student.value=frm.student.value+"A"
end sub
sub add_b_onclick
frm.student.value=frm.student.value+"B"
end sub
sub delete_onclick
if frm.student.value<>"" then
frm.student.value=left(frm.student.value,len(frm.student.value)-1)
end if
end sub
//-->
</SCRIPT>
<form name=frm>
<input name="student" type="text">
<input type="button" name="add_a" value="A">
<input type="button" name="add_b" value="B">
<input type="button" name="delete" value="删除">
</form>