Como sumar dos textbix

Buen dia expertos :
me pueden ayudar tengo que sumar dos textbox tengo algo como esto
Private Sub ComboBox1_Click()
Dim i As Integer
Dim j As Integer
Dim final As Integer
Dim FINAL2 As Integer
For i = 2 To 1000
If Hoja5.Cells(i, 1) = "" Then
final = i - 1
Exit For
End If
Next
For i = 2 To 1000
If Hoja6.Cells(i, 1) = "" Then
FINAL2 = i - 1
Exit For
End If
Next
For i = 2 To final
If ComboBox1 = Hoja5.Cells(i, 1) Then
TextBox1 = Hoja5.Cells(i, 2)
TextBox8 = Hoja5.Cells(i, 3)
TextBox6.Text = Val(TextBox6.Text) * 0.16
TextBox7.Text = Val(TextBox4.Text) + Val(TextBox6.Text)
Exit For
End If
Next
For j = 1 To FINAL2
If ComboBox1 = Hoja6.Cells(j, 1) Then
TextBox8 = Hoja6.Cells(j, 3)
Exit For
End If
Next
End Sub