Add calculated text to ordinate dimension

Hello!  I'm hoping someone can help me.  Currently, when I do drawings, I give my machinists drawings with each point, and they program their machines.  To do that, they calculate the round part diameters, which is basically 5" - 2x<Dim>.   

I'd like it if I could give them drawings with the real number, and in parenthesis next to it, 5-2x<Dim>.  

 I've attached a jpg of what I normally give them and how I'd like it to look. Is this something do-able via a macro or something?  Thanks in advance

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