I compile ConTeXt out of NP++ with the following command in the Execution-Plugin:
cd $(CURRENT_DIRECTORY)
context.exe "filename.tex" --synctex=1
taskkill /im SumatraPDF.exe
C:\somedirectory\sumatra.bat "$(CURRENT_DIRECTORY)\filename.pdf"
This command compiles the context-file and opens it in the PDF-reader Sumatra. As you see, I close the reader ("taskkill") and restart it again with every compile.
But that is not necessary, Sumatra updates the pdf-file by its own. So how to change the command, such that the reader will be only started, if it is not already started?