[Silgraphite-fonts] Graphite font questions

[A BC <eg...@gm...>]

Hello,

my name is Jon Brown and I am using graphite to program a font to behave
correctly and I want to code the following effects, can you provide me with
suggestions:

(These two involve "smart" diacritics behavior)
1. If there is no base character, then diacritics mark will not display. I
want diacritics mark to lock if first condition is not met. In other words,
if the user presses a diacritics key and if the previous character is not a
base character then the diacritics will not appear on the screen.

2. If there is already a base character followed by a diacritics then I
want,
   then next diacritics to not display. I don't want diacritics overlapping.

If the above cannot be achieved with font, can it be accomplished with
programming a keyboard such as Tavultesoft keyman?