Populating usrFields from Project Task to Time Activity

I have been attempting to update 2 Boolean field values on Time Activity based on the same usr fields in the PM-Task Table.  So when a time card has the project Task with “OnSite” Checked or “Travel” Checked it will carry over to the Time Card.  Once created I plan to use this to create fields to match Billable and Total Billable on the Time cards.  I understand that is best done with Event Handlers and maybe this would have been as well.  This is my first time working with Attributes and I have tried to write this a number of ways but somehow I am missing something.  My code is below if anyone has any ideas.

PMTask
{
  public class PMTaskExt : PXCacheExtension<PX.Objects.PM.PMTask>
  {
    #region UsrIsOnsite
    [PXDBBool]
    [PXUIField(DisplayName="IsOnsite")]

    public virtual bool? UsrIsOnsite { get; set; }
    public abstract class usrIsOnsite : PX.Data.BQL.BqlBool.Field<usrIsOnsite> { }
    #endregion

    #region UsrIsTravel
    [PXDBBool]
    [PXUIField(DisplayName="IsTravel")]

    public virtual bool? UsrIsTravel { get; set; }
    public abstract class usrIsTravel : PX.Data.BQL.BqlBool.Field<usrIsTravel> { }
    #endregion
  }
}

PMTimeActivity
{
  public class PMTimeActivityExt : PXCacheExtension<PX.Objects.CR.PMTimeActivity>
  {
    #region UsrIsOnsite
    [PXDBBool]
    [PXUIField(DisplayName="Onsite")]
    [PXFormula(typeof(Switch<
      Case<Where<
        PMTask.taskID, Equal<Current<PMTimeActivity.projectTaskID>>,
        And<PMTask.projectID, Equal<Current<PMTimeActivity.projectID>>>>,
        PMTaskExt.usrIsOnsite>,
        PMTaskExt.usrIsOnsite>))]


    public virtual bool? UsrIsOnsite{ get; set; }
    public abstract class usrIsOnsite: PX.Data.BQL.BqlBool.Field<usrIsOnsite> { }
    #endregion

    #region UsrIsTravel
    [PXDBBool]
    [PXUIField(DisplayName="IsTravel")]
    [PXFormula(typeof(PMTaskExt.usrIsTravel))]
        [PXFormula(typeof(Switch<
      Case<Where<
        PMTask.taskID, Equal<Current<PMTimeActivity.projectTaskID>>,
        And<PMTask.projectID, Equal<Current<PMTimeActivity.projectID>>>>,
        PMTaskExt.usrIsTravel>,
        PMTaskExt.usrIsTravel>))]
    public virtual bool? UsrIsTravel { get; set; }
    public abstract class usrIsTravel : PX.Data.BQL.BqlBool.Field<usrIsTravel> { }
    #endregion
  }
}