You need two text box(Text1 Text2), one Label(Label1)
and two Command box(Command1 Command2).

Private Sub Command1_Click()
Value1 = Val(Text1.Text)
Value2 = Val(Text2.Text)
v = Value1 + Value2
Label1.Caption = CStr(v)
End Sub

Private Sub Command2_Click()
Text1.Text = ""
Text2.Text = ""
Label1.Caption = " "
End Sub

Source Calculator 1.5

Private Sub Command1_Click()
Value1 = Val(Text1.Text)
Value2 = Val(Text2.Text)
v = Value1 + Value2
Label1.Caption = CStr(v)
End Sub

Private Sub Command2_Click()
Text1.Text = ""
Text2.Text = ""
Label1.Caption = " "
End Sub