i got an error >>> Arithmetic operation resulted in an overflow.

please help

thanks in advance

```
Private randomClass as new Random
For i = 0 To CInt(10) - 1
strId &= Mid(strCodes, Int(Len(strCodes) * randomClass.Next() ) + 1, 1)
Next
For i = 0 To CInt(4) - 1
strId2 &= Mid(strCodes, Int(Len(strCodes) * randomClass.Next() ) + 1, 1)
Next
```