Simple, the problem is for the price list, if you can modify the price list you should change the currency money, but more efective is go to the database in the table res_currency and find the id of your money for example USD id = 3, then find table product.pricelist and change the value in currency_id for the new id, it's all. 

But you before have that change the parameters in accounting -> configuration -> change type money and Configuration -> company -> change type money.

This way is more effective when you implement ecommerce.

The currency of your sale order and purchase order are the currency of the pricelist your customer or supplier is linked to.

If you the CHF is the currency linked to your company, your default sale and purchase pricelist are also in CHF

Create a new pricelist, in USD, and link your supplier to this pricelist
 

Yes sure you can go on your customer and tell price liste in USD.. so if you take thist custumer it will creat the USA currency. hope it will help you ... 

Custumer then sale and purchases  and down left you will find it :) just recreat your  SO and you will have it in USD ... even your SO you can put them in germand in frensh in english etc with cheking language... and then in your product you have to set the translations ... etc 

hope you  have engout info  

Thanks for the answers. But actually I didn't give enough informations.

If I go to Purchase, Quotation, and then select a supplier which is using USD price list there is no problem the CHF field changes to USD.

But, if I go to Sales, Sales order and select a product for which the supplier is using USD price list, confirm the sale. Then automatically a Purchase Quotation is created. In this one the currency field will be CHF, even the supplier is using USD price list.

Any idea ?

You have to enable pircelist support in Settings before you can use it.

Marek Mosiewicz

http://consultantodoo.com