Fetch value from a table equal-greater or equal-less according to expression.

[cmano]

Hello guys i use these expressions (boxplots-whiskers)

Top whisker (tw) :

FractileExc(If(Characteristic='γ',Value), 0.75) + 1.5*(FractileExc(If(Characteristic='γ',Value), 0.75)-FractileExc(If(Characteristic='γ',Value), 0.25))

Low whisker (lw): 

FractileExc(If(Characteristic='γ',Value), 0.75) + 1.5*(FractileExc(If(Characteristic='γ',Value), 0.75)-FractileExc(If(Characteristic='γ',Value), 0.25))

I have these results from above expressions : 19.62375 (tw) & 7.93375 (lw).

For tw i want ta fetch the first equal less value from the result i.e 17

For lw i want ta fetch the first equal greater value from the result i.e 8.4

Table:

For your reference Note that table is not sorted and i have plenty of Process order & characteristics.

Any advise??