I have a simple query which returns a number of fields, including
DOUBLE PRECISION. A grid is used to edit the data. To my surprise, I
found that the input of characters into the numeric fields is
generally disabled, but the grid allows the characters E I N and T to
be entered. I have no idea of what this may be good for (despite E
perhaps, for "123E+4") and would like to supress it. Entering "ii"
or "3i" results in an error message ("not a floating point value").

I tried to figure out an edit mask, but the field contents is just a
general floating point. What would be the proper way?

Mirco