I have written many tutorials on the different methods to inject a dll into a process here at ZoneHacks.  These DLL Injection tutorials, however, never covered Visual Basic. Continue reading if you would like to find out how!

Below is everything you need to inject a dll into a target process:
Option Explicit On Error goto error ' just to cover our ass if there is an unexpected error. Public Type SECURITY_ATTRIBUTES nLength As Long lpSecurityDescriptor As Long bInheritHandle As Long End Type Public SA as SECURITY_ATTRIBUTES Public Const PAGE_READWRITE as long = &h4 Public Const MEM_COMMIT as long = &h1000 Public Const MEM_RELEASE as long = &h8000 Public Const PROCESS_ALL_ACCESS As Long = (STANDARD_RIGHTS_REQUIRED Or SYNCHRONIZE Or &HFFF) Public Function InjectDll(Dll as String, target as String) As Boolean Dim hWnd as long ' Stores handle of target window Dim hLoadLibraryA as long ' Stores handle to loadlibrary Dim hThread as long ' Stores handle to remote thread Dim hRemoteMem as long ' Stores handle to remote memory Dim hProcess as long ' Stores handle to target process Dim procID as long ' Stores Process ID Dim dwBytesWritten as long ' Stores number of bytes written Dim dwThreadID as long ' Stores remote thread id ' Initialize security attributes SA.nLength = Len(SE) SA.lpSecurityDescriptor = False ' Find the target window hWnd = FindWindow(target, vbNullString) GetWindowThreadProcessId hWnd, procID ' This will get the process id and store in procID ' Open the existing process object hProcess = OpenProcess(PROCESS_ALL_ACCESS, False, procID) if hProcess = 0 then goto error ' Get the proc address of LoadLibrary hLoadLibraryA = GetProcAddress(GetModuleHandle("kernel32.dll"), "LoadLibraryA") ' Commit a region of memory within the virtual address space of the target process hRemoteMem = VirtualAllocEx(hProcess, 0, LenB(Dll), MEM_COMMIT, PAGE_READWRITE) if hRemoteMem = 0 then goto error ' Write our dll into the memory we committed. WriteProcessMemory hProcess, ByVal hRemoteMem, ByVal Dll, LenB(Dll), dwBytesWritten ' Create a thread that runs in the virtual address space of the target process hThread = CreateRemoteThread(hProcess, SA, 0, ByVal hLoadLibraryA, ByVal hRemoteMem, 0, dwThreadID) if hThread = 0 then goto error ' Wait until the thread is in the signaled state or the time out interval elapses WaitForSingleObject hThread, 1000 VirtualFreeEx hProcess, hRemoteMem, 0&, MEM_RELEASE Exit Function error: MsgBox "An error has occured!", "VB Injection ERROR!", MB_ERROR End Function

Hope this has helped you all =)   Have fun!