frmchlid引用字段找不到

如题，在用软件写代码是出现的错误提示，求解。以下是完整的编码

Private Sub CmdSave_Click()
Dim rst As Object
Dim strSQL As String
Dim MaxID As String
Dim currentID As String
Dim strFrm As String
If IsNull(Me.txtSupName) Then
    MsgBox "请输入有效的供应商名称！", vbCritical, "提示"
    Me.txtSupName.SetFocus
    Exit Sub
    End If
MaxID = DMax("[SupID]", "tblCodeSup")
currentID = "G" & Format(Val(Right$(MaxID, 3) + 1), "000")
strSQL = "select*from tblCodeSup"
Set rst = CurrentDb.OpenRecordset(strSQL, dbOpenDynaset)
rst.addnew
rst!SupID = currentID
rst!SupName = Me.txtSupName
rst.update
rst.Close
Set rst = Nothing
Me.txtSupName = Null
DoEvents
strFrm = Form_FrmSup_sg_Main!frmChild.SourceObject
Form_FrmSup_sg_Main!frmChild.SourceObjece = srtFrm
MsgBox "您输入的数据已保存！", vbInformation, "消息"
End Sub