ve se é assim que voce esta fazendo....
cria a chamada de uma lib...
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
no evento do seu textbox colocar
espero ter ajudado