请教:如何将子窗体中的某个文本型字段的值用"+"连接起来

能否明示一下,

Dim strTemp As String
Dim frm As Form
Dim ctls As Controls
Set frm = Me.产品材料信息子窗体.Form
Set ctls = frm.Controls
For i = 1 To frm.RecordsetClone.RecordCount
    frm.SelTop = i
   strTemp = ctls("品名规格").Value & strTemp 是不是这里不对,我改了很多次也没对.
    MsgBox srtTemp
Next i
Me.txtPM = srtTemp