Input string was not in a correct format

[laven1]

Not sure of how to resolve this error... See below...

Dim btnZero As Integer = 0
    Dim btnOne = 1
    Dim btnTwo = 2
    Dim btnThree = 3
    Dim btnFour = 4
    Dim btnFive = 5
    Dim btnSix = 6
    Dim btnSeven = 7
    Dim btnEight = 8
    Dim btnNine = 9
    Dim intCounter As String = 0
    Dim numberArray() As String
    Dim comboString As String
    Dim myDec As Decimal
 
Private Sub btnDecimal_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDecimal.Click
 
'The purpose of the code below is to store button clicks into an array as a
'string so they can be joined and viewed in a rich text box.  The below button 
'is for the decimal.  I thought I could store it in the array and then convert 
'the string number, including the decimal as a number... so I could do
'calculations.
 
        ReDim Preserve numberArray(intCounter)
        Dim btnDecimal As String = "."
        numberArray(intCounter) = btnDecimal
        rtbScreen.Text = numberArray(intCounter)
        intCounter = intCounter + 1
        Console.WriteLine("The Decimal button was pressed")
        Console.WriteLine("intCounter =" & intCounter)
        comboString = String.Join("", numberArray)
        Console.WriteLine("Value of comboString =" & comboString)
        myDec = Convert.ToDecimal(comboString) 'Here is my error
        rtbScreen.Text = comboString
 
    End Sub

Thanks,

Joe