How to limit choices in cart quantity

My client has a product which can be ordered in only 3 quantities: 1, 3, or 5.
On the cart page the Quantity text box accepts any amount. How can I limit the customers choices to change it to only 1, 3, or 5?

make a note of the name of the quantity text box. then delete it and replace it with a select list.

Set the name of the select list to the same as the text box that you just deleted, and set the values for the select list to use 1,3 or 5

I see how that works, but I'm still doing something wrong in the code, because when I make a different choice, it just reverts back to the original quantity.

Here's what I have:

<td class="eC_FormItem">
<select name="coffeeCart_Quantity_<?php echo $coffeeCart->DisplayIndex; ?>" >
<option value="1">1</option>
<option value="3">3</option>
<option value="5">5</option>
</select></td>

Obviously this is very wrong, since it always displays 1 even when the input page sent 3.

the list wont show the quantity you selected to add to the cart, the cart will show the selected quantity.

How can I have it do both, the original amount and then the new updated amount?

I dont understand what you mean, once the quantity is in the cart, the list will just revert back to the original selections.

The quantity list is there to show what _can_ be selected, not what has been selected. go to the cart display page to see what quantity _has_ been selected.

Sorry If I've not been clear. What I need is to have a customer select, 1 on the input page, they then click "add to cart", the cart page is displayed and the quantity 1 is displayed and the appropriate price is charged. But when they're on the cart page they may decide to change their order to 3 (with the dropdown list), click "update", and 3 should be displayed and the price will become thrice what it was.

OK, On the ccart page, you need to replace the quantity text box with an eCart updateable list.

remove the existing quantity filed in the cart display, then go to Insert -> ecart -> Updateable List, set the cart column to quantity.

I tried that originally, but if it's an updatable list, aren't I back to the same problem of someone entering an odd number, like 7? I guess I don't understand what are the possibilities with an updatable list.