Access: Test a string for an alphanumeric value

Question:  In Access, I want to know if a string value contains alphanumeric characters only. How can I do this?

Answer:  To accomplish this, you need to create a custom function.

You'll need to open your Access database and create a new module.

Then paste into the new module the following function:

Function AlphaNumeric(pValue) As Boolean

    Dim LPos As Integer
    Dim LChar As String
    Dim LValid_Values As String

    'Start at first character in pValue
    LPos = 1

    'Set up values that are considered to be alphanumeric
    LValid_Values = " abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ+-.0123456789"

    'Test each character in pValue
    While LPos <= Len(pValue)

        'Single character in pValue
        LChar = Mid(pValue, LPos, 1)

        'If character is not alphanumeric, return FALSE
        If InStr(LValid_Values, LChar) = 0 Then
            AlphaNumeric = False
        Exit Function
        End If

        'Increment counter
        LPos = LPos + 1

    Wend

    'Value is alphanumeric, return TRUE
    AlphaNumeric = True

End Function

The AlphaNumeric function will return TRUE if all of the values in the string are alphanumeric. Otherwise, it will return FALSE.

You can use the AlphaNumeric function as follows:

AlphaNumeric("6.49")	would return TRUE
AlphaNumeric("^Tech on the Net ")	would return FALSE
AlphaNumeric("hi~there")	would return FALSE