arcpy.CalculateField_management(tabl, tabl+".De_cs","tt1(!"+tabl+".Helyrajziszam!,!"+shp+".Helyrajziszam!,!"+shp+".Qel_real_cs!",kiftipus,t1)
t1="""def tt1(hsz, Helyrajziszam,Qel_real_cs) .... """

table is the linked table, shp is the original table. hsz == Helyrajziszam will be true even if their order is not the same? Because of the linking, right?