Hello Guessed,
i tried your code. It workes fine but its still not works they way i want it to. I have an external software which can check and uncheck this Checkbox, but the problem i is that it ony changes the value from the checkbox.

I tried the Document_ContentControlBeforeStoreUpdate (which should work with my software) but i am just getting the error message from my first post. (Runtime error 6197: This object model error is not available in the current event.)

This ist the code i tried:

Private Sub Document_ContentControlBeforeStoreUpdate(ByVal ContentControl As ContentControl, Content As String)

If ContentControl.Tag = "Checkbox1" Then
ContentControl.Parent.Bookmarks("Test1").Range.Fon t.Bold = ContentControl.Checked
End If

End Sub

You guys maybe have a solution for me?