Looked into RTD for a bit today. RTD is a Microsoft Excel function provided by Microsoft. Developers can create COM servers that feeds data to the RTD function in Excel spreadsheets. TOS created a COM server for the RTD function. From what I can see, the VB source code for the RTD function is not available to the public so creating an interface that talks directly to the TOS COM server is likely very difficult to impossible. If I created software that needs to communicate with a RTD COM server, I would look to use an Excel library as the client side is a closed-source Excel function.