childs lock possible on these cars?

[kikkegek]

hi guys,

my oldest daughter, 3 years now, is old enough to open car doors (of course). That is why she now rides in the middle of the back seat in her kid-seat.

but within a couple of weeks she will be to old and big for the seat and she will be allowed to just use the normal seat and belt with a little seat like this:



I will put 3 point belts in the back, but also wanna make sure she isnt able to open the back doors by herself.

is there a way to put some kind of childslock on the back doors?

any idea's? or somebody did this?