COMPUTERNAME

Returns the full computer name of where the code is running.
For instructions on how to add a function to a workbook refer to the page under Inserting Functions

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

Function ReturnComputerName() As String 
Dim sBuffer As String * 255 
Dim lLength As Long 
Dim sComputerName As String 

    sComputerName = "" 
    lLength = GetComputerName(sBuffer, 255) 
    lLength = InStr(1, sBuffer, Chr(0)) 
    If (lLength > 0) Then 
        sComputerName = Left(sBuffer, lLength - 1) 
    Else 
        sComputerName = sBuffer 
    End If 

    ReturnComputerName = UCase(Trim(sComputerName)) 
End Function 

The full computer name can be seen from (Start > Control Panel > System)(Computer Name tab).