Evaluating VAR through skill

I have a variable that retrieves stop time from ADE-L or ADE-XL session. Based on that I do some post processing. This flow breaks if user sets the stop time as a variable like VAR("stoptime").
This is what I am trying to do.

-          Open ADE-L, set transient stop time to 1u.

-          In CIW, type

                  a = asiGetCurrentSession()

b = a~>data~>analysis~>data~>tran~>data~>fields~>data~>stop~>value
 

-          This should return “1u”

-          In my code, I do something like,

if(evalstring(b) < 50e-09 then <do something>

-          This flow works perfectly fine.
 

-          Now, set stop time to  VAR(“stoptime”) and execute the above commands. “b” will retuns something like "VAR(\"stoptime\")"
 

-          evalstring(b) returns nil for this case and hence the entire code breaks.
 

Is there a way to handle this scenario?

Thanks.