Just a simple reminder time addition?

[rumplestiltskin]

When I add an appointment I can set an alarm for "x" before the time I've set (1 min, 5 min, 15 min, 30 min, 60 min, 1 day, etc.). What I need, however, is a 90 minute setting between the 60 min and 1 day setting.

I have a registry editor installed on my phone but don't have a clue which entry should be modified. My phone is a Motorola Q9m running WM6.

Any help will be appreciated (and I'll buy you a beer if you're in the neighborhood).

Thanks!