Plugin Help with Public/Protected Voids??

Hi guys, I'm a bit at a loss here. I've never ventured into how these voids work and I need to use variables from one in the other. I want this plugin to only run when 1 of 3 specific people update a Task. The plugin fails if anyone else does it because they don't have permissions to the regarding entity. So I want to catch it and only run with specific people use it.

I found some code that demonstrates how to get the current user id but I'm having issues getting it to work. I get an error message that says 'TaskUpdate.JobCostUpdate.PostTaskUpdate.Execute(System.IServiceProvider)' hides inherited member 'TaskUpdate.JobCostUpdate.Plugin.Execute(System.IServiceProvider)'. Use the new keyword if hiding was intended.'

Code is below. Thanks for any help.

namespace TaskUpdate.JobCostUpdate
{
    using System;
    using System.Linq;
    using System.ServiceModel;
    using Microsoft.Xrm.Sdk;
    using Microsoft.Xrm.Sdk.Client;
    using Microsoft.Xrm.Sdk.Query;

    public class PostTaskUpdate : Plugin
    {
        Guid jocelyn = new Guid("ABD80D9F-F3B8-E211-AC09-12A32B1E376A");
        Guid trevor = new Guid("E200F73B-57CC-E111-B35F-12A32B1E376A");
        Guid Lois = new Guid("2B13D49B-BD82-E311-990D-12A32B1E376A");
        Guid userId;
        public PostTaskUpdate()
            : base(typeof(PostTaskUpdate))
        {
            base.RegisteredEvents.Add(new Tuple<int, string, string, Action<LocalPluginContext>>(40, "Update", "task", new Action<LocalPluginContext>(ExecutePostTaskUpdate)));

        }

        public void Execute(IServiceProvider serviceProvider)
        {
            IPluginExecutionContext context = (IPluginExecutionContext)serviceProvider.GetService(typeof(IPluginExecutionContext));
            IOrganizationServiceFactory serviceFactory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
            userId = context.InitiatingUserId;
        }

        protected void ExecutePostTaskUpdate(LocalPluginContext localContext)
        {
            if (localContext == null)
            {
                throw new ArgumentNullException("localContext");
            }
            IPluginExecutionContext context = localContext.PluginExecutionContext;
            IOrganizationService service = localContext.OrganizationService;

            var ServiceContext = new OrganizationServiceContext(service);
            ITracingService tracingService = localContext.TracingService;

            if (context.InputParameters.Contains("Target") &&
            context.InputParameters["Target"] is Entity)
            {
                if (userId == trevor || userId == Lois || userId == jocelyn)
                {
                    Entity entity = (Entity)context.InputParameters["Target"];
                    Entity pEntity = service.Retrieve("task", entity.Id, new ColumnSet("new_billingtaskid"));
                    string postImage = "";

                    if (pEntity.Attributes.Contains("new_billingtaskid"))
                    {
                        postImage = (string)pEntity["new_billingtaskid"];
                    }

                    if (entity.Attributes.Contains("new_billingtaskid"))
                    {
                        postImage = (string)entity["new_billingtaskid"];
                    }

                    var res = from q in ServiceContext.CreateQuery("new_salescommissionslineitems")
                              where q["new_billingtask"].Equals(entity.Id)
                              select q;

                    foreach (var q in res)
                    {
                        q["new_jobcostid"] = postImage;
                        ServiceContext.UpdateObject(q);
                    }
                }
                ServiceContext.SaveChanges();
            }
        }
    }
}