I have two sub-forms within this navigation form are (Employees) and other named (Clients)
I think you have one subform control and as you click on the tab you navigate to the selected form as is common with navigation form. Follow the code below -
navigationform is main form,NavigationSubform is subform control on it. Form3 is one of the forms on main form having field to which you wish to set focus
Code:
Private Sub Text4_LostFocus()
Forms!navigationform!NavigationSubform.SourceObject = "Form3"
Forms!navigationform!NavigationSubform.SetFocus
Forms!navigationform!NavigationSubform!Text0.SetFocus
End Sub