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 OpenFile()
    ShellExecute 0&, vbNullString, "c:\Имя файла.pln", vbNullString, vbNullString, vbNormalFocus
End Sub

Sub CAD()
    Dim Programm As String, files As String
    Programm = "c:\CAD.exe"
    files = "c:\Имя файла.pln"
    Shell """" & Programm & """ """ & files & """", vbNormalFocus
End Sub

Sub PDFOpen()
            'Открываем программу, которая открывает документ
            Programm = "c:\Program Files\Foxit Software\Foxit Reader\Foxit Reader.exe"
            
            'Указываем адрес файла
            Files = "c:\jrc4558.pdf"
            
            'Открываем Файл
            Shell Programm & " " & Files, vbNormalFocus
        End Sub 

Sub CAD()
    Dim Programm As String, files As String
    Programm = "Путь\.EXE"
    files = ThisWorkbook.Path & Application.PathSeparator & i & "Файл.pln"
    Shell """" & Programm & """ """ & files & """", vbNormalFocus
End Sub