Hi Stephen,
Thanks for providing us details,
We will look into it and get back to you soon.
Thank you.
We have supported it. You can calculate the Subtotal function through custom calculation implementing ICustomFunction interface. Kindly try the Aspose.Cells version 4.5.0.3 posted @: http://www.aspose.com/community/forums/thread/134097/support-for-replace-function-in-.net.aspx