Keep getting this error sometimes when mid is ZERO: 

> 
> Invalid procedure call or argument: 'Mid'
> 
> 
> 

How would I fix this?

```
Function CreateRandomString(iSize)
    Const VALID_TEXT = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
    Dim sNewSearchTag
    Dim I

    For I = 0 To iSize
        Randomize
        sNewSearchTag = sNewSearchTag & Mid(VALID_TEXT,Round(Rnd * Len(VALID_TEXT)),1)
    Next

    CreateRandomString = sNewSearchTag
End Function

```