PayPal add to cart button - lower shipping on multiple items (in drop down list)
I would like to have a non-hosted PayPal add to cart button with a drop down box for multiple color options (green, blue, red). I would like the first quantity added to the cart using this button (example: green) to add $4.00 S&H. Then, I'd like any additionals (for example red), regardless of what color, to add only $0.50 to the total S&H.
I'm already using the variable shipping2=0.50 in the button's form code, however the $0.50 shipping only applies when more than one of the same color is added. So, for example if I add one green, then one red, from this same button, the shipping ends up being $8.00 instead of the $4.50 I want.
Please provide some options for how to solve or workaround this problem without using a full store backend. I have tried instead looking at using just the "Shipping Calculations" in my PayPal profile, however as far as I can tell, this only allows 5 different shipping costs, which is very limiting with different sizes/weights/quantities of items.