So the subprogram is a procedural COBOL program that resides in a different project is that correct?
Is the project containing the called program a managed code Class Library project or is it a native project?
Is FPACTGN the name of the Class Library project?
If not then you might have to load the projects .dll prior to calling the entry point.
Please take a look at the tutorial here which covers using the CALL statement within in managed code projects in Visual COBOL for Visual Studio.
Thanks.