How kill executables started with spawnShell or executeShell when program finish?

[Marcone]

Becouse my program use plink.exe running with spawnShell or 
executeShell.
But when my program finish with some crash, or killed with 
windows task manager by user, Plink still running. How can I stop 
all process initialized with spawnShell or executeShell when 
program finish? I another works, how can I make plink.exe only 
lives when program is running?