[VB] Noob need Help

Hello guys, I am creating simple calculator in VB. My problem is when I multiply two numbers and I get their answer I want to multiply that answer to another number.

Code:

Private isMultiplying As Boolean = False

Private Sub btnMultiply_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMultiply.Click
        If txtNum1.Text.Length <> 0 And txtNum2.Text.Length <> 0 And isMultiplying = False Then
            Dim answer As Double = multiply(CType(txtNum1.Text, Double), CType(txtNum2.Text, Double))
            txtAnswer.Text = answer.ToString()
            txtNum2.ReadOnly = True
        ElseIf isMultiplying = True Then
            Dim ans As Double = multiply(CType(txtNum1.Text, Double), CType(txtAnswer.Text, Double))
            txtAnswer.Text = ans.ToString()
        Else
            MessageBox.Show("Unesite brojeve u polja", "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning)
        End If

Private Function multiply(ByVal num1 As Double, ByVal num2 As Double) As Double
        Return num1 * num2
    End Function

Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
        revertBool()
    End Sub

Private Sub revertBool()
        isMultiplying = False
    End Sub

    End Sub

And now if I multiply 5 * 5 I get 25 which is good, and then I want to enter again num1 to another number ex. 2 then I want to get 50,but I get 10 ????
Sorry If this is confusing !

Thanks!

 

Oh I figure it out. I didn't set isMultiplying = True before ElseIf statement