You probably apply like this :
var Path = System.Web.Hosting.HostingEnvironment.ApplicationPhysicalPath;
if (!System.IO.Directory.Exists(Path + "\\ExcelFiles"))
{
System.IO.Directory.CreateDirectory(Path + "\\ExcelFiles");
}
var logFilePath = Path + "\\ExcelFiles";
This will create a folder inside your server deployed path...which will always access from the server where you have placed all dll's. So your server related issue is gone.