Loop through a string to find the odd numbers VB - vba

Question

I am looping through a card number finding all the odd numbers and multiplying them by the card digits. Its kind of hard to explain. I am having trouble multiplying the odd number and the card number. Here's an example my teacher gave me. You multiply card number 1 and and odd number 1 and so forth. I am not getting any errors, it just kind of freezes.
Sums
Card #: 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
Multiples 1 2 3 4 5 6 7 8
Evens: 2 4 6 8 0 2 4 6 32 =Sum 1
Odds: 1 6 15 28 45 6 21 40 162 =Sum 2
Sum 3: 194
194 =Sum 3
Step 4: =1+9+4 = 14
= 1 + 4 = 5 = check digit
Public Class Payment
Private Sub OK_Click(sender As Object, e As EventArgs) Handles OK.Click
Dim Sum1 = 0
Dim Sum2 = 0
Dim Sum3 = 0
Dim ready As Boolean
Dim ccnumb = CardNumber.Text
Format(CardNumber.Text, "################")
Dim exp = Mid(ExpDate.Text, 1, 3)
Dim checkdigit = 0
If FullName.TextLength = 0 Or cardtype.Text.Length = 0 And ccnumb.Length <= 16 Or exp.Length = 2 Then
MessageBox.Show("Please enter all credit card information before proceeding.")
ready = False
Else ready = True
End If
If ready = True Then
For Each num As Char In ccnumb
If CInt(CStr(num)) Mod 2 <> 0 Then
Sum1 += CInt(CStr(num)) * CInt(CStr(num)) Mod 2 <> 0
Else
Sum2 += CInt(CStr(num))
End If
Next
Sum3 = Sum1 + Sum2
Do While Sum3 > 10
For j = 0 To Sum3.ToString.Length - 1
For k = 1 To Sum3.ToString.Length - 1
Sum3 = j + k
Next
Next
Loop
Do While exp.Length > 1
checkdigit = Mid(ExpDate.Text, 1, 1) + Mid(ExpDate.Text, 1, 2)
Loop
If Sum3 = checkdigit Then
MessageBox.Show("Congratulations! Your payment was successful.")
CustInv.Show()
Else MessageBox.Show("The checkdigit," & Space(1) & Sum3 & Space(1) & "does not match the month code," & Space(1) & checkdigit & "." & Space(1) & "Please reenter your card information.")
End If
End If
End Sub

Answer 1

"it kind of freezes" is lay speak for "my code enters an infinite loop".
This looks suspicious:
Do While Sum3 > 10
For j = 0 To Sum3.ToString.Length - 1
For k = 1 To Sum3.ToString.Length - 1
Sum3 = j + k
Next
Next
Loop
To enter the loop, Sum3 must be greater than 10. For the loop to exit, Sum3 must not be greater than 10, but your code only increments Sum3, so Sum3 can only stay greater than 10.
This means that once entered, this loop is infinite.

Answer 2

If changing outer loop to inside loop doesn't help you
Try this
Do While Sum3 > 10 and j < sum3 ' adding j < sum3 might stop the loop
For j = 0 To Sum3.ToString.Length - 1
For k = 1 To Sum3.ToString.Length - 1
Sum3 = j + k
Next
Next
Loop