Calling Subs When Workbook Opens

I have the following code in a module that I would like to initiate when the workbook opens:

Code:
Private Declare Function GetComputerName Lib "kernel32" _
Alias "GetComputerNameA" ( _
ByVal lpBuffer As String, _
ByRef nSize As Long) As Long

Public Property Get ComputerName() As String

[Code] ........

In a worksheet, I have =compname() in cell A1 and =hdserialnumber() in A2. What is the trick to make the values in these cells appear as soon as the worksheet opens?