How to open a grasshopper file from the same working folder as Rhino

I want to open a Grasshopper file that lies in the same folder as my Rhino file with a Rhino button. What I have sofar is as below, it requires the full path of grasshopper which is not ideal for my case.

Command for Rhino Button:

-_Grasshopper
: Banner
: Disable
-_Grasshopper _Document
: Close
: Enter
-_Grasshopper _Document _Open “C:*full path of GH file”
: Enter

Anyone knows if it is possible to achieve this in the commandline or has used other workarounds? Thank you in advance.