Toolkit for creating editable grid

I want to create editable grid (client application) for large Postgres
table:

At startup this grid show first screenful of records and allows to edit
them.
When user presses page down key, this grid should read next screenful of
records and allow to edit them etc.
PgADMIN tries to read the whole table.

Is there any free toolkit or sample application for this ?

Andrus.