L_Shift + R_Shift combination undistinguishable

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I actually came here to find some recent way(s) to contact Michael with the following problem only to find out he presumably passed away (see https://www.reddit.com/r/programming/comments/8hq332/til_what_happened_to_michael_scott_kaplans_blog/ and http://archives.miloush.net/michkap/archive/index.html ).

Therefore I will ask here about it - maybe @therealdreg or @CodeVisio would know something.

Some 6 years ago a need emerged to map the combination L_Shift + R_Shift as a new modifier switching to a third level. Note an individual shift switches only to a second level. I soon realized this is problematic if not impossible to achieve with a layout DLL.

Simply because a layout DLL translates scan codes to virtual key codes but special keys like both ctrls, both alts, and Shifts are being treated as one virtual key - in my case shift. Thus I can not use the combination `L_Shift + R_Shift`` at all because the kernel code would either ignore them or do something different than third level.

Any insight how could this be achieved?