Very likely your DataWindow object isn't being compiled into the EXE.
When you compile an EXE, PowerBuilder starts at the Application object and intelligently tries to determine which objects should be included. Since d_plateaccessions is only referenced in a string in a script, it isn't included.
There are two ways around this.
You can create a PBD for the PBL containing the DataWindow. PBD creation blindly includes all objects in the PBL. This method is quite popular, and many people just mark all their PBLs for PBD creation and deploy the PBDs.
You can alternatively create a PBR for the EXE, telling the compiler to force certain DataWindows and graphic files into the EXE. If you really want a single EXE, but don't want the effort of building an appropriate PBR, you can use PBL Peeper to generate PBRs and scripts to force all DataWindows and objects (and find all relevant graphics) into a compiled EXE, using the PBR Builder Plus report.
Good luck,
Terry.