How to change fields values in editable grid faster using only keyboard?

Hello colleagues,

I would like to ask some help with fields in editable grid. I have an editable Grid Area Window with two columns (one field is read only and other editable).
When I am using my mouse, everytime I am clicking on that editable field (moving through the records), it focuses on that field: marks whole text if there is any and I can type in it. That's great.
But everytime I am selecting that field using only keyboard (e. g. pressing DOWN key), that field is selected, but not focused, i. e. I have to either press LEFT key and RIGHT key or click with mouse in that field to change value.

What I would like to do is to be able to change field's value instantly after pressing DOWN key (or something like that).

I am using TS 3.4.0 version.

Any help would be very appreciated.

Thank you.