通过未绑定文本框为Outlook.MailItem添加附件时触发Error 438

我能发送带附件的邮件，但只有附件路径硬编码时才正常运行，代码如下：

With olMail
    .To = Me.EmailTo
    .CC = Me.EmailCC
    .Subject = Me.EmailSubject
    .BodyFormat = olFormatPlain
    .Body = Me.EmailMessage
    .Attachments.Add "C:\Users\pat.lewis\Desktop\description.docx"
    .Send
End With

我的表单上有个名为LinkedFile1的未绑定文本框，赋值代码是：

Me.LinkedFile1 = "C:\\Users\\pat.lewis\\Desktop\\description.docx"

但当我把Me.LinkedFile1的值传给.Attachments.Add时，代码无法运行：

With olMail
    .To = Me.EmailTo
    .CC = Me.EmailCC
    .Subject = Me.EmailSubject
    .BodyFormat = olFormatPlain
    .Body = Me.EmailMessage
    .Attachments.Add Me.LinkedFile1 '无法运行！！
    .Send
End With

该行代码会触发如下错误：

error 438: Object doesn't support this property or method

.Attachments.Add Me.LinkedFile1

就算把Me.LinkedFile1的值赋给字符串变量再引用，还是不行：

Dim olAttachment1 As String

If IsNull(Me.AttachedFile1) = False Then
    olAttachment1 = Me.LinkedFile1
End If

With olMail
    .To = Me.EmailTo
    .CC = Me.EmailCC
    .Subject = Me.EmailSubject
    .BodyFormat = olFormatPlain
    .Body = Me.EmailMessage
    .Attachments.Add olAttachment1 '还是无法运行！！
    .Send
End With

内容的提问来源于stack exchange，提问作者Pattrick Lewis