Multiple Dynamic Drop-Downs

I am sure this will be a doozy.

here's what I have:
http://test.apenloversparadise.com/untitled.asp

it is generated via the following table structure:

tableName
icID <- INT(4) identity
parentID <-INT(4)
invCat <-NVARCHAR(255)

i need to have multiple drop-downs, for the depths of the categories (it's a hierarchal category system)

so:
if the data in the table contains

1   0   Games
2   0   Music
3   1   Doom
4   1   Quake
5   3   Doom I
6   3   Doom II
7   5   Soundtrack

then I need to have:
1st drop-down containing:
<option value="1">Games</option>
<option value="2">Music</option>

if Games is selected, a second drop-down should appear:
<option value="3">Doom</option>
<option value="4">Quake</option>

if Doom is selected in the second one, then a 3rd needs to be displayed containing:
<option value="5">Doom I</option>
<option value="6">Doom II</option>

and so on down the list.  This may get pretty deep in the hierarchy, so it needs to allow for an unlimited depth, trick is once the 3 drop-downs are there, if I go back to the 1st and select Music, the process should start all over again generating the next drop-down, etc...

I am not oppose to an AJAX solution or straight javascript solution, however it would need to be cross-browser compatible

here is the code I currently have to generate the drop-down on the link above:
<script language="javascript" runat="server">
function jssort(a)
{
   return (new VBArray(a)).toArray().sort().join(String.fromCharCode(0));
}
</script>
<%
Sub write(strString)
      response.write(strString)
End Sub
inrsConn = "myConnectionString"
class invcat
   dim id, category, parentid, description
end class
class invcats
   dim cats
   dim sortindex()  'holds sorted key index
   sub class_initialize
        set cats = server.createobject("Scripting.Dictionary")
   end sub
   sub class_terminate
        set cats = nothing
   end sub
   sub BuildFromDB(connstr)
       LoadFromDB connstr
       SetLabels
       BuildSortIndex
   end sub
   sub BuildFromArray(array)
       LoadFromArray array
       SetLabels
       BuildSortIndex
   end sub
   sub LoadFromArray(a)
       dim i,n,line,cat
       for i = lbound(a) to ubound(a)
            line = split(a(i),"^")
            set cat = new invcat
            cat.id = line(0)
            cat.parentid = line(1)
            cat.category = line(2)
            cats.add cat.id, cat
       next
   end sub
  sub LoadFromDB(conn)
        dim rs, cat
        set rs = server.createobject("ADODB.Recordset")
        rs.open "select icID, parentID, invCat from invCat", conn
        do while not rs.eof
            set cat = new invcat
            cat.id = rs("icID")
            cat.parentid = rs("parentID")
            cat.category = rs("invCat")
            cats.add clng(cat.id), cat
            rs.movenext
        loop
        rs.close
        set rs = nothing
   end sub
   sub SetLabels
      dim i
      for each i in cats.keys
          cats(i).description = mid(BuildLabel(i),4)
      next
   end sub
   function BuildLabel(id)  
       if id = 0 then
          BuildLabel = ""
          exit function
       else
          dim curcat
          set curcat = cats(id)
          BuildLabel = BuildLabel(curcat.parentid) & " - " & curcat.category
       end if
   end function
   sub BuildSortIndex
       dim key,descripts,desc
       set descripts = server.createobject("Scripting.Dictionary")
       for each key in cats.keys
           desc = cats(key).description
           if descripts.exists(desc) then
              descripts(desc) = descripts(desc) & "|" & key
           else
              descripts(desc) = key
           end if
       next
       dim sorted
       sorted = split(jssort(descripts.keys), chr(0))
       dim i,n,keys,index
       index = 0
       redim sortindex(cats.count - 1)
       for i = lbound(sorted) to ubound(sorted)
           keys = split(descripts(sorted(i)), "|")
           for n = lbound(keys) to ubound(keys)
              sortindex(index) = keys(n)
              index = index + 1
           next
       next
   end sub
  function SelectBox
        dim i,out,cat
        out = "<select name=""cat"">" & vbcrlf
        for i = lbound(sortindex) to ubound(sortindex)
           if cats.exists(clng(sortindex(i))) then
           set cat = cats(clng(sortindex(i)))
                out = out & "<option value=""" & cat.id & """>" & cat.description & vbcrlf
        end if
        next
        out = out & "</select>" & vbcrlf
        SelectBox = out
   end function
end class
dim myCats
set myCats = new invcats
myCats.BuildFromDB(inrsConn)
%>
<br>
<br>
New Drop-Down<br>
<%= myCats.SelectBox %>