https://hosopro.blogspot.com/2017/09/access-vba-form-property.html

フォーム1＞

‘メンバ変数
Private mRetnValue As String

‘プロパティ
Public Property Let RetnValue(ByVal Value As String)
mRetnValue = Value
End Property

Public Property Get c() As String
RetnValue = mRetnValue
End Property

---

Private Sub buttonOpen_Click()

mRetnValue = ""

DoCmd.OpenForm "フォーム2", acNormal, , , , acDialog

'フォーム2で選択した値をテキストボックスに表示
Me.textMessage.Value = mRetnValue

End Sub

フォーム2＞

Private Sub buttonOK_Click()

Form_フォーム1.RetnValue = Me.comboFruits.Value

DoCmd.Close acForm, Me.Name

End Sub