Adding Modifiers to Concentration Roll

First time DM here, I am designing a spellcaster for my campaign using the NPC sheet and was wondering if there was a way to add their INT modifier specifically just to concentration checks. I read about macros but I am not 100% sure if this would be the solution or if there is an easier one. Any help would be greatly appreciated.

What game are you playing and which character sheet are you using? If you’re not sure please supply a screenshot. 

I'm playing 5e and using the character sheet 2014 to make the character, though I'm using the NPC sheet if this makes a difference

Ttabbo,  To clarify Jarren's question, there are 10 D&D 5e character sheets on Roll20. Nine of them are "2014" rules.  Are you using the "D&D 5e 2014 by Roll20" character sheet? If so, I would make an ability (add a section in the left column) and add the roll there as an inline roll. [[1d20 + @{npc_con_save} + @{intelligence_mod}]] (Assumes intelligence is being added to the Constitution saving throw. 

Just tried this and it worked perfectly, thank you so much