possible for specific USPS shipping options to be shown based on cart quantity?

[zippygaloo]

Is it possible to have specific USPS flat rate shipping options automatically appear based solely on the quantity of items being purchased? I sell very small items and the small USPS flat rate boxes will only hold four max. The medium USPS flat rate boxes will hold around 50 more. The large USPS box will hold around 75. Here's an example of what I need...

1 item  = "X amount" shipping (in a small USPS flat rate box)
2 items = "X amount" shipping (in a small USPS flat rate box)
3 items = "X amount" shipping (in a small USPS flat rate box)
4 items = "X amount" shipping (in a small USPS flat rate box)
5-50 items = "X amount" shipping (in a medium USPS flat rate box)
50-75 items = "X amount" shipping. (in a large USPS flat rate box)