Adding a Minus-Sign to an Arrowhead

[Pooya <Input Pooya de>]

Hello, dear people,

having in mind to build a signal flow sheet, I would like to know, if it is possible to have a minus-sign 
snapping to an arrow head?

Usage: If you want to substract a signal from another, you use the conjunction symbol (+) with a minus-sign 
beside the arrowhead of the substrahend.

Thank you very much.