Create View from command line

Hi

I'm trying to build a Windows Form application that needs to alter the
definition of a View, depending on user input/selection. Essentially,
the user is selecting a property of known coordinates ('x','y') and
setting a 'buffer' distance . I then want to retrieve the records which
represent the map features within the specified distance of the
property. The WHERE clause of my view is:

st_dwithin(mytable.geom, st_setsrid(st_point(x, y), 27700), buffer);

I'm thinking this could be achieved either by making x, y and buffer
parameters or, I simply ALTER the View statement with literal values.
Whichever, I need to do this from a command line attached to a windows
form event, e.g. button_click.

I cannot work out how to do this. Can anyone point me in the right
direction. I've looked at psql.exe, but can't work out if this holds the
answer.

Thanks

Oisin