Processes running under Windows Task Manager?

[glb][/glb] how does the DOS command looks like if I were to detect if a particular process is currently running as shown by the Task Manager?
for eg., if I launch the calculator and saw calc.exe process running as shown by the Task Manager, but when I run a simple DOS batch file with something like :

if exist calc.exe (
echo Running
)

but it doesn't work...which DOS command should I use then? or, what path should I specify for calc.exe or etc processes seen in the Task Manager??

Any helpful advise?