Macro Question - Mongoose Traveller 2nd Edition Character Sheet

I am using the Mongoose Traveller 2nd Edition Character Sheet. I am creating a macro that needs to reference a Skill Specialty. Meaning that you have the Base Skill and you can add specialty skills as a sub-skill under the base skill.  In my specific macro, I am trying to reverence a specialty skill of Melee called Unarmed. Not all characters will have the specialty skill of Unarmed, in which case I would like it to default to the base Melee skill. Any assistance would be greatly appreciated. Here is what I have so far... &{template:default} {{name= Melee-Grapple }} {{attacker= @{selected|token_name} }} {{defender= @{target|token_name} }} {{Margin= [[(2d6 + @{selected|Melee} + ?{Attacker Modifier|0}[MOD]) - (2d6 + @{target|Melee} + ?{Defender Modifier|0}[MOD])]]}}