使用标准的WebServices是不可能的,但是您可以用这样的方法编写自己的WS:
  
  [WebMethod]
public void FixFileData(string fileUrl, DateTime created, DateTime modified, string author, string editor)
{
  Guid siteId = SPContext.Current.Site.ID;
  Guid webId = SPContext.Current.Web.ID;
  try
  {
    SPSecurity.RunWithElevatedPrivileges(delegate
    {
      using (SPSite site = new SPSite(siteId))
      {
        using (SPWeb web = site.OpenWeb(webId))
        {
          SPFile file = web.GetFile(fileUrl);
          SPListItem fileItem = file.Item;
          fileItem[SPBuiltInFieldId.Created] = SPUtility.CreateISO8601DateTimeFromSystemDateTime(created.ToUniversalTime());
          fileItem[SPBuiltInFieldId.Modified] = SPUtility.CreateISO8601DateTimeFromSystemDateTime(modified.ToUniversalTime());
          try
          {
            fileItem[SPBuiltInFieldId.Author]=web.EnsureUser(author);
          }
          catch (Exception)
          {
          // Your loggin code
          }
          try
          {
            fileItem[SPBuiltInFieldId.Editor] = web.EnsureUser(editor);
          }
          catch (Exception)
          {
          // Your loggin code
          }
          fileItem.UpdateOverwriteVersion();
          if (fileItem.ParentList.EnableMinorVersions)
          {
            file.Publish("SPFileUpload");
          }
          if (fileItem.ModerationInformation != null)
          {
            file.Approve("SPFileUpload");
          }
        }
      }
    });
  }
  catch (Exception)
  {
  // Your loggin code
  }
}