FB 1.5; no additional function added form a DLL

I would like to run the following SQL but TRUNC is not a function. Is there a way to get around this (NAllow is a float)?

Update MyData set
NewAllow = Trunc(NAllow),
New2Allow = Trunc((NAllow - Trunc(NAllow)) * 10);

What I have is data like this:

NAllow NewAllow New2Allow
10.1 10 1
5.3 5 3
7.0 7 0
0.4 0 4

Can something like this be done in a SQL command?

Thank you,

Ed Dressel