ccnumber$ = visaPrefixList$(Rand)

ccnumber$ = visaPrefixList$((Rand(1,9))

SeedRnd MilliSecs()
Dim visaPrefixList$(9)


visaPrefixList$(1) = "4539"
visaPrefixList$(2) = "4556"
visaPrefixList$(3) = "4916"
visaPrefixList$(4) = "4532"
visaPrefixList$(5) = "4929"
visaPrefixList$(6) = "40240071"
visaPrefixList$(7) = "4485"
visaPrefixList$(8) = "4716"
visaPrefixList$(9) = "4"

Print credit_card_number("visa",16,3)
WaitKey


Function completed_number(prefix$, length)
   
    ccnumber$ = prefix$
   
   
    While  Len(ccnumber$) < (length - 1)
        ccnumber$ = ccnumber$+Rand(0,9)
    Wend
   
   
   
    sum = 0
    pos = 1
   
    reversedCCnumber$ = strrev(ccnumber)
   
    While pos < length - 1
      
        odd = Mid(reversedCCnumber$,pos,2);
        If odd > 9
            odd = odd-9
        EndIf
      
        sum = sum + odd
      
        If pos = (length - 2)
      Else
         
            sum = sum + Mid(reversedCCnumber,pos+1,1)
        EndIf
        pos = pos+2
    Wend
   
   
   
    checkdigit = (( Floor(sum/10) + 1) * 10 - sum) Mod 10
    ccnumber$ = ccnumber$ + checkdigit
   
    Return ccnumber
   
End Function


Function credit_card_number(prefixList$, length, howMany)
   
   Select prefixList
         
      Case "visa"
         For i=0 To howMany Step 1
            ccnumber$ = visaPrefixList$(Rand(1,9))
            result = completed_number(ccnumber$, length)
         Next
         
         
   End Select
   
   
   
   Return result
   
End Function



Function strrev(zahl$)
   
   For I=(Len(zahl$)) To 1 Step -1
      fertig$=fertig+Mid(zahl$,I,1)
   Next
   
   Return fertig
   
End Function