You could always add the value as an attribute
Dim MainContent As ContentPlaceHolder = TryCast(Master.FindControl("MainContent"), ContentPlaceHolder)
Dim _usercontrol As UserControl = CType(Page.LoadControl("~\Usercontrols\dashboard_Employer.ascx"), Control)
MainContent.Controls.Add(_usercontrol)
_usercontrol.Attributes.Add("Value", "1")
In your user control you could set
Public Property ValueID() As Integer
Get
Return If(Me.Attributes("ValueID").Length < 1, 0, CType(a.Attributes("ValueID"), Integer))
End Get
Set(ByVal value As Integer)
Me.Attributes.Add("ValueID", value.ToString())
End Set
End Property