窗體也是類，所以類中響應窗體自定義事件也是可以的...

不過樓主的程式碼邏輯有問題，程式碼也有問題，類要建立例項才行：

"----------------------- "窗體程式碼：-----------------------

Option Explicit

"宣告事件

Public Event LoginRequest(ByVal userid As String)

"宣告啟動事件的過程

Public Sub StartTest()

RaiseEvent LoginRequest("123456")

End Sub

"例項化類

Private Sub Command1_Click()

Dim cls As Class1

Set cls = New Class1

End Sub

"-----------------------------------------------------------

"------------------------ "類程式碼 --------------------------

Option Explicit

Public WithEvents mLogin As Form1

"響應窗體Form1的事件

Private Sub mLogin_LoginRequest(ByVal userid As String)

mLogin.Text1.Text = userid

End Sub

"例項化mLogin，並執行mLogin.StartTest方法

Private Sub Class_Initialize()

Set mLogin = Form1 "指向Form1,不能用new...

mLogin.StartTest

End Sub

"-----------------------------------------------------------