variable inside variable?

[GoSooJJ]

I have number of item IDs. The format is like
qty_<itemID>
qty_111
qty_112
qty_113
....

When the form is submitted, I then take that qty_<itemID> to get values by looping the items by using ItemID. I have hard time to figure out how to get value of the qty_111. This is more like variable inside variable. I tried this way but didn't work.

<c:if test=&quot;${not empty paramValues.update_id}&quot;>
<c:forEach var=&quot;cartID&quot; items=&quot;${paramValues.update_id}&quot;>
${param.qty_${cartID}}
</c:forEach>
</c:if>

Can I do this?