Binaryworld - BitClear - Clear a bit in a value ... [ VB -> Math ]

Function BitClear(ByVal value As Long, ByVal bit As Long) As Long
  ' simply AND with the negation of the bit mask
  ' Range checking is performed in Power2()
  BitClear = (value And Not Power2(bit))
End Function

' Raise 2 to a power
' the exponent must be in the range [0,31]

Function Power2(ByVal exponent As Long) As Long
  Static res(0 To 31) As Long
  Dim i As Long

  ' rule out errors
  If exponent < 0 Or exponent > 31 Then Err.Raise 5

  ' initialize the array at the first call
  If res(0) = 0 Then
    res(0) = 1
    For i = 1 To 30
      res(i) = res(i - 1) * 2
    Next
    ' this is a special case
    res(31) = &H80000000
  End If

  ' return the result
  Power2 = res(exponent)

End Function