crystal report – group by sahred variable from subreport

I”m working with crystal report version11.
I build a main report that calls to sub report , there is a shared variable that get his value in the sub report.
I can see the value of the variable in the main report.
I want to group by the data in the main report according to the share variable ( who gets it’s value from the sub report ), when I activate the browse data ( in the main report ) it shows no values althought it shows the value in the main report .

Another symptom that althought the value is displayed in the main report i can’t see it in the group options.
I tried to define it in another formula field but it didn’t work.
Is it possible to group by a variable that get it’s value in the sub report ? and how ?