For example, this string:

    Some test (text) with wierd ;-) characters + more!

becomes this:

    Some+test+%28text%29+with+wierd+%3B%2D%29+characters+%2B+more%21

' Return a URL safe encoding of txt.
Private Function URLEncode(ByVal txt As String) As String
Dim i As Integer
Dim ch As String
Dim ch_asc As Integer
Dim result As String

    SetSafeChars

    result = ""
    For i = 1 To Len(txt)
        ' Translate the next character.
        ch = Mid$(txt, i, 1)
        ch_asc = Asc(ch)
        If ch_asc = vbKeySpace Then
            ' Use a plus.
            result = result & "+"
        ElseIf m_SafeChar(ch_asc) Then
            ' Use the character.
            result = result & ch
        Else
            ' Convert the character to hex.
            result = result & "%" & Right$("0" & _
                Hex$(ch_asc), 2)
        End If
    Next i

    URLEncode = result
End Function

Private m_SafeChar(0 To 255) As Boolean
' Set m_SafeChar(i) = True for characters that
' do not need protection.
Private Sub SetSafeChars()
Static done_before As Boolean
Dim i As Integer

    If done_before Then Exit Sub
    done_before = True

    For i = 0 To 47
        m_SafeChar(i) = False
    Next i
    For i = 48 To 57
        m_SafeChar(i) = True
    Next i
    For i = 58 To 64
        m_SafeChar(i) = False
    Next i
    For i = 65 To 90
        m_SafeChar(i) = True
    Next i
    For i = 91 To 96
        m_SafeChar(i) = False
    Next i
    For i = 97 To 122
        m_SafeChar(i) = True
    Next i
    For i = 123 To 255
        m_SafeChar(i) = False
    Next i
End Sub