Well, it looks the control you are using is an ActiveX control and we only preserve it as it is in XLS/XLSX files, we don’t support to manipulate it (get / set its properties). I think you for the time being may use Label or some other Form Control using Aspose.Cells. Please see the following documentation link for details of different controls supported by Aspose.Cells:<o:p></o:p>
As per the original post, unfortunately we are unable to use other types as these files already exist out "in the wild" so we have to recover the data from them somehow.
I look forward to a fix as it would push Aspose beyond the competition.