Modify web config programmatically to a certain or specific web application

Hi,

i work in an IT consultant and currently i'm having a problem in depolying sharepoint 2010 solution.

the solution which i created require the web config of the targeted web application to be modified, however this must be done programmatically during the deployment using WSP.

i have tried several solutions which i found but all of them is leading to modifying all web config in the application pool, i don't want that to happen because the target is only 1 web application.

the piece of code that i use already point to the specific web application but still when i deploy the solution, all web config files are affected.

here is the piece of code that i use :

public override void FeatureActivated(SPFeatureReceiverProperties properties)
{
    SPWebService service = SPWebService.ContentService;
    SPWebConfigModification myModification = new SPWebConfigModification();

    SPSite site = new SPSite("http://win-a52s8epvot4:888/");
    SPWeb web = site.OpenWeb();

    myModification.Path = "configuration/appSettings";

    myModification.Name = "add[@key='SQLArchiveConnectionString'][@value='Data Source=WIN-A52S8EPVOT4;Initial Catalog=TRAEmployee;User ID=sa;Password=P@ssw0rd;Persist Security Info=False;']";

    myModification.Sequence = 0;
    myModification.Owner = "administrator";
    myModification.Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode;
    myModification.Value = "<add key='SQLArchiveConnectionString' value='Data Source=WIN-A52S8EPVOT4;Initial Catalog=TRAEmployee;User ID=sa;Password=P@ssw0rd;Persist Security Info=False;' />";
    web.Site.WebApplication.WebConfigModifications.Add(myModification);
    service.Update();
    service.ApplyWebConfigModifications();
}

need advise or help urgently...

regards,

-WN-

-Regards- Willy Noviandy