on the LostFocus event of the text box, set the tab to 2. You'd probably want to put in some checking to be sure that the user really put in informtation where he/she should.
Private sub LastText_LostFocus()
' check to see if the information's filled in
If Len(Text1.Text) > 0 and Len(Text2.Text) > 0... Then
SSTab1.Tab = 1
End If
Keep in mind that the tabs start at 0, not 1.
Happy programming!
~Melissa