LinuxQuestions.org - ISO_Level3_Shift level triggered by keyboard layout change

Usually in my linux-debian system i use Ctrl and shift to change my layout from 'us' to greek and reverse .

But after creating a custom ~/.Xmodmap now pressing Ctrl + Shift
while in greek i pass to ISO_Level3_Shift level and then if i press Ctrl + Shift i pass again to the USA layout.

Code:

$ xmodmap -pm 

xmodmap:  up to 4 keys per modifier, (keycodes in parentheses):



shift      Shift_L (0x32),  Shift_R (0x3e)

lock        Caps_Lock (0x42)

control    Control_L (0x25),  Control_R (0x69)

mod1        Alt_L (0x40),  Alt_R (0x6c),  Meta_L (0xcd)

mod2        Num_Lock (0x4d)

mod3      

mod4        Super_L (0x85),  Super_R (0x86),  Super_L (0xce),  Hyper_L (0xcf)

mod5        ISO_Level3_Shift (0x5c),  Mode_switch (0xcb)