Link Character sheet attribute to another character sheet?

Sorry if this has been answered already, a quick search didn't locate the info I need. I am still new to macro programming and I am trying to figure out if it is possible to link an attribute on one character sheet to an attribute on another without API access?  I am trying to create a character sheet for a Genie Warlock's (from TCoE) vessel. The vessel's AC is equal to the warlock's spell save dc.  @{character's name|spell_save_dc} doesn't work.  (edited to clarify query used)

This isnt correct format; @{character_name|spell_save_dc} you need to include the characters actual name (like Bob, Frodo the Barbarian, or whatever), or selected or target , but you can only use the last two if using tokens. character_name can only be used on the other side of the |, like @{selected|character_name} when its the character name you want to display, and want to grab it from the character linked to a token.

Sorry if I wasn't clear. I was actually using the character's name, not a placeholder. Also to clarify I'm using the default 5E OGL page. When I type it into the ac field on the attributes page it just shows the query text not the actual number in the ac field of the core page. 

Some fields are not designed to allow lookup values or formulas.

keithcurtis said: Some fields are not designed to allow lookup values or formulas. That's kind of what I suspected, but I wanted to make sure I wasn't missing something obvious. Thanks. BTW, I've been blowing my friend's (our regular DM for over a year) mind with all the "stupid tricks" I've been finding on the forum. Thanks for the work on that.