attribute and dropdown question

Hello.
I need to use multiple attributes for single Item . so I will have to create many Dropdowns on single product detail.
problem that i m having is that , first value in dropdown is always selected. so if customer add one attribute , other attributes from other dropdown will be added.

there is option to disable that using option or check box .. but i can not find the option for dropdown.

I would appreciate if anyone can tell me how to fix this .

thanks.

Explain your "multiple attributes"

I have products that are different sizes. such as 50 ml, 100ml, 250ml, up to 2000 ml..
they are all come in packages of 12, 24, etc..

each size is option name and each packaging is option value
ex: 50ml : pkc 12
pkc 24
pkc 96

no in this example pkc 12 is always selected. if i add other sizes to same products detail page. than the first value in all dropdowns are selected by default.
I only want the user select attribute(s) they want ..

thanks.

I think tht you need to create a space keeper attribute for these and give it first sort order priority.

One like "Select" with no adds to the price etc. This one will show first but not add to the cost

And I think you can mark this one as: Used For
Display Purposes Only: