Instead of setting a reference to the textbox's .TextFrame.TextRange, set it to the new shape itself, then
With tbox1.TextFrame.TextRange
.Text = "hello"
.Font.Bold = True
End With
With tbox1.Fill
.Visible = True
.ForeColor.RGB = RGB(255,255,255)
end with
With tbox1.Line
.Visible = True
.ForeColor.RGB = RGB(0,0,0)
.Weight = 2
End With