ok, i changed the decimal filed types to double and then converted the db to access 97 format

I don't have the Round Function give me two expresion for this two field in the query:
m: Conmutador([pocet]>0 Y [plus]>0;Round(([druhy_rozmer]/100*[pocet]+[plus]/100)*[prvy_rozmer]/100*[dlzka];3);[pocet]>0 Y ([plus]=0 O EsNulo([plus]));Round([prvy_rozmer]/100*[druhy_rozmer]/100*[dlzka]*[pocet];3);([pocet]=0 O EsNulo([pocet])) Y [plus]>0;Round([prvy_rozmer]/100*[plus]/100*[dlzka];3))

c: Conmutador([pocet]>0 Y [plus]>0;Round(Round(([druhy_rozmer]/100*[pocet]+[plus]/100)*[prvy_rozmer]/100*[dlzka];3)*[jedn_cena];1);[pocet]>0 Y ([plus]=0 O EsNulo([plus]));Round(Round([prvy_rozmer]/100*[druhy_rozmer]/100*[dlzka]*[pocet];3)*[jedn_cena];1);([pocet]=0 O EsNulo([pocet])) Y [plus]>0;Round(Round([prvy_rozmer]/100*[plus]/100*[dlzka];3)*[jedn_cena];1))

Ok, let's simplify: these two fields are now removed from the query and from the subform too - the error is the same ("Reserved Error")...

With this change in Access 97 work very fine.
I only change the Me.Requery for Forms![doklad_rezivo]![doklad_rezivo_riadok].Requery
I send your sample base with the Update.

Hello Guys,
I am Oracle Database administrator, however i am unable to administrate access database .
All i want is to SELECE (FNAME, SNAME, LNAME and EGN) in the SubForm based on that script:

SELECT Students.FName, Students.SName, Students.LName, Students.EGN
FROM T1_Specialnost INNER JOIN (T1_Period INNER JOIN (T1_Groups INNER JOIN Students ON T1_Groups.Group_ID = Students.Group_ID) ON T1_Period.Period_ID = Students.Period_ID) ON T1_Specialnost.Spec_ID = Students.Spec_ID
WHERE (((T1_Specialnost.SpecName)=[Forms]![Start]![Combo0]) AND ((T1_Groups.GroupName)=[Forms]![Start]![Combo2]) AND ((T1_Period.PeriodDate)<=[Forms]![Start]![Combo6]));

However it seems that, i am unable to requery to subform even when your comments.
Could you please help me please ?