Using Loops - Please help

I'm killing myself over here. I'd appreciate any help offered.

I'm trying to write a program that will sum values in this series (ð/4=1-1/3+1/5-1/7+1/9-...) and print the estimate for ð. I would like for the user to choose whether to sum 100, 200, 300, 400, or 500 values to estimate ð. The more values that are added, the closer the sum *4 will be to 3.1416.

Thank you for your help.

Will this do ?

Code:

---

Option Explicit
Dim sigma As Double
Dim doAdd As Boolean

Private Sub Command1_Click()
    doAdd = True
    sigma = 0
    If (Text1.Text <> "") Then
        If (IsNumeric(Text1.Text)) Then
            Dim i As Long
            For i = 3 To Text1.Text Step 2
                If (doAdd) Then
                    sigma = sigma + (1 / i)
                Else
                    sigma = sigma - (1 / i)
                End If
                doAdd = Not doAdd
            Next i
            sigma = 1 - sigma
            sigma = 4 * sigma
            MsgBox "Answer : " & sigma
        End If
    End If
End Sub

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