Attribute problems, PLEASE HELP

[sonat]

i am using zen cart 1.3.9d
i have the product grid mod add on

my problem is with attributes, ihave searched this site high an low and none of the suggestions help me.

here is what i wish to do...

i have a product lets call is ptroduct A

product A is 20" long and the price is $10

i want to offer it as a 22" version with the price being 10% more
and i want to offer is 24: version with the price being 20% more

i have tried many different things and the prices make no sense...

please assume i am a complete dummy and give me the instructions to do this.

i am pretty sure the instructions that you give me is something i have already tried.. at this point i am assuming it might be a problem with the code.

[sonat]

a bit more information regarding the problems i am having with the attributes...

i have item A at a length of 20" with a base price of $20

then i have a 50% sale so the product price is $10 on sale

i have added an attribute of 22" and want to sell this at 10% more

so i have marked the price factor as 1.10

the following occures on the on the product page...

on the choose length dropdown box that i have the item shows a price of $11 for the 22" length (which is the $10 sale price plus the 10% add on) which is correct!

BUT when i add to cart and go to check out... it calculates the 22" price incorectly.

what it does is take the original presale price of the 20" add to it10% and then it adds the sale price of the 20" on top of that

meaning

the 20" = $20 original price presale
1.10 x $20 = $22
$22+$10 = $32

the 22" is $32 in the shopping cart instead of $11

was i clear on this???

[sonat]

okay after more investigating i have solved a few things and found out a few more things....

as it stands right now... i have the base price and i have the price factor and offset adjusted to compensate for the price changes i want to make...

the only problem left is...

it is using the tax before it calculates the price factor when it ads to cart

example

product A is 20" long and priced $20
product A 22" version is 10% higher set up with the price factor

now what the cart is doing is:

it is taking the $20 from product A 20" and adding 13% provincial tax to ist then it is adding the 10% from the price factor increase

there for the amount on the cart is incorrect becuase.. when i go to check out and enter my address it ads the provincial tax again...

was i clear on this and can anyone help?