Trying to write a function to calculate commission

[cbruckman2006]

Ok here is what I am doing. I have to develop a program that determines how much a salesperson makes. Here is the following instructions:

A salesperson earns a weekly base salary plus a commission when sales are at or above quota. Create a project that allows the user to input the weekly sales, and teh salesperson name, calculates the commission, and displays summary information.

Write a function procedure to calculate the commission. The function must compare sales to the quota. When the sales are equal to or greater than the quota, calculate the commission by multiplying sales by the commission rae. Each salesperons receives the base pay plus the commission (if one has been earned).

I am having trouble developing a function. I have most of the code for the calculate button coded. Here is what I have so far. When the calculate button is pushed it must output the commission(if one is earned), total sales adn the total pay earned.

'Program Name       Chapter5ExtraCredit
'Programmer         Chad R. Bruckman
'Date               10/15/2006
'Description        A salesperson earns a weekly base salary
'                   plus a commission when sales weekly sales 
'                   are at or above quota.
Public Class salesForm
    'Declare module-level variables for summary information.
    Dim totalCommissionDecimal, totalsalesDecimal, totalpayDecimal As Decimal
    Dim salesCountInteger As Integer
 
    'Declare constants
 
    Const QUOTA_Decimal = 1000
    Const COMMISSION_RATE_Decimal = 0.15F
    Const BASE_PAY_Decimal = 250D
 
    Private Sub calculateButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles calculateButton.Click
        'Calculate and display the current amounts and add to totals.
        Dim totalPayDecimal, totalAmountDecimal As Decimal
 
        With Me
            'Calculate the total pay.
            With Me
                Try
                    salesCountInteger = Integer.Parse(.weeklySalesTextBox.Text)
 
                    totalPayDecimal = FindCommission(BASE_PAY_Decimal)
 
 
                    .commissionTextBox.Text = totalCommissionDecimal.ToString("N")
                    .totalSalesTextBox.Text = salesCountInteger.ToString("D")
                    .totalPayTextBox.Text = totalPayDecimal.ToString("C")
                Catch quantityException As FormatException
                    MessageBox.Show("Input must be numeric.", "Data Entry Error", _
                    MessageBoxButtons.OK, MessageBoxIcon.Information)
                    With .weeklySalesTextBox
                        .Focus()
                        .SelectAll()
                    End With
                End Try
            End With
        End With
    End Sub
 
    Private Function FindCommission(ByVal totalCommissionDecimal As Decimal) As Decimal
        If QUOTA_Decimal >= salesCountInteger Then
            Return salesCountInteger * COMMISSION_RATE_Decimal
        Else
            Return BASE_PAY_Decimal
        End If
    End Function
 
 
End Class