>>542 ずいぶんと面倒くさい事を >513 は無視して俺流で書いてみた。
ボタン→フォーム→クラス→DLL作成元とイベントが伝わるからめんどい。
{prjDllTest}
[Class1]
Option Explicit
Private WithEvents m_oForm1 As Form1
Public Event FormButtonClicked(nButton As Long)
Private Sub Class_Initialize()
　　Set m_oForm1 = New Form1
　　Call m_oForm1.Show
End Sub
Private Sub m_oForm1_ButtonClicked(nButton As Long)
　　RaiseEvent FormButtonClicked(nButton)
End Sub
[Form1]
Option Explicit
Public Event ButtonClicked(nButton As Long)
Private Sub Command1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
　　RaiseEvent ButtonClicked(CLng(Button))
End Sub
{prjDllTestTest}
[Form1]
Option Explicit
Private WithEvents m_oDllTest As prjDllTest.Class1
Private Sub Form_Load()
　　Set m_oDllTest = New prjDllTest.Class1
End Sub
Private Sub m_oDllTest_FormButtonClicked(nButton As Long)
　　Debug.Print "CLICKED!!!"
End Sub