在Visual Basic（VB）中，要禁用或关闭某个程序，你可以使用API函数来查找和发送关闭消息给该程序的窗口，或者直接结束该程序的进程。以下是几种方法：
使用`FindWindow`和`PostMessage` API函数
使用`FindWindow`函数查找程序窗口的句柄（hwnd）。
使用`PostMessage`函数发送关闭消息（WM_CLOSE）给该窗口。
示例代码：
```vb
Option Explicit
Private Declare Function FindWindow Lib "User32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function PostMessage Lib "User32" Alias "PostMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Private Const WM_CLOSE = &H10
Sub CloseProgram(ByVal programName As String)
Dim winHwnd As Long
winHwnd = FindWindow(vbNullString, programName)
If winHwnd <> 0 Then
PostMessage winHwnd, WM_CLOSE, 0, 0
Else
Debug.Print "Window not found."
End If
End Sub
```
使用任务管理器
通过任务管理器（Task Manager）查找并结束程序的进程。
你可以通过VB的`Shell`对象调用系统命令`taskkill`来结束进程。
示例代码：
```vb
Option Explicit
Private Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" (ByVal hwnd As Long, ByVal lpOperation As String, ByVal lpFile As String, ByVal lpParameters As String, ByVal lpDirectory As String, ByVal nShowCmd As Long) As Long
Sub KillProgram(ByVal programName As String)
Dim pid As String
pid = GetProcessId(programName)
If pid <> "" Then
ShellExecute 0, "taskkill", "/F /PID " & pid, "", "", 1
Else
Debug.Print "Process not found."
End If
End Sub
Function GetProcessId(ByVal processName As String) As String
Dim proc As Object
Set proc = GetObject("winmgmts:{impersonationLevel=impersonate}!//" & _
".\\root\\cimv2:Win32_Process.Name='" & processName & "'")
GetProcessId = proc.ProcessId
End Function
```
使用`App.PrevInstance`防止多个实例运行
通过检查`App.PrevInstance`属性来防止同一程序的多实例运行，但这并不直接关闭已运行的程序，而是防止新实例的启动。
请注意，关闭程序可能会受到操作系统权限的限制，特别是当程序以管理员权限运行时。此外，强制关闭某些系统关键进程可能会导致系统不稳定或数据丢失，因此请谨慎使用这些方法。
