Update list items with Web request values

Hi Everybody,

I have a workflow which querries a webservice from our system to get customer informations like Name, CustomerNo and Street. This workflow create a list item for every customer. This works very fine.

Now I want to update every customer in the list, with the new querried values from the web request, for example every day. 

I tried to querry the customer list in sharepoint, take the result in a collection to update every record with the querried values, but it doesn't work.

Does anyone have a solution for this problem?

thanks!

Marc