how do API's work?

hey all i can call on API's in visual basic cant i?
and how do i do it
how would i get the following cod to work(and yes i do no stuff needs to be replaced with proper servers and stuffs)

#define UNICODE
#define MESGLEN 50
WCHAR awcToName[] = TEXT("DomainName*");
WCHAR awcFromName[] = Text("MyComputer");
WCHAR awcMesgBuffer[MESGLEN] = Text("This ia Test Message");
NET_API_STATUS nasStatus;

nasStatus = NetMessageBufferSend(NULL,
awcToName,
awcFromName,
awcMesgBuffer,
MESGLEN);

i just wanna no how i would actualy make this work!
do i need controls can some one send a for with it working on plz
thanx
TrAcER

Two things:
1. get the apiveiwer & api-guide from www.allapi.net.
Free. Good.

2. Looks like something from MSDN. Here is VB code for the same api call (from guess where?:

Code:

---

Private Declare Function NetMessageBufferSend Lib _
  "NETAPI32.DLL" (yServer As Any, yToName As Byte, _
  yFromName As Any, yMsg As Byte, ByVal lSize As Long) As Long
Private Const NERR_Success As Long = 0&
Public Function SendMessage(RcptToUser As String, _
  FromUser As String, BodyMessage As String) As Boolean
 
  Dim RcptTo() As Byte
  Dim From() As Byte
  Dim Body() As Byte

  RcptTo = RcptToUser & vbNullChar
  From = FromUser & vbNullChar
  Body = BodyMessage & vbNullChar

  If NetMessageBufferSend(ByVal 0&, RcptTo(0), ByVal 0&, _
        Body(0), UBound(Body)) = NERR_Success Then
    SendMessage = True
  End If

End Function
Private Sub Form_Load()
    'Example created by X-MaD ([email protected])
    'Visit his website at http://www.zolnetwork.com/x-mad
    Dim RetVal As Boolean
    RetVal = SendMessage("Utente", "FromUser", "BodyText")
End Sub

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