Need help with Column Measure to restrict data

I use the following measure as a filter on my Column Chart, so I can Show Items when the value is less than or equal to what ever number of months I want.    I use a count +0 to show zero data months.  What can I add to the measure as a Var to restrict months to a start date field I have for each company but allow 60 months if company had Start Date over 5 yearsa go.       

My current issue is that, if I select 6 months with the measure filter, but company Start Date is only two years back, I see 40 months of zeros I don't want.