question about the use of bfloat



Hello,
I asked this kind of question before in a less specific way.  Maybe 
there is a better answer to the question as posed in this message.

 I am developing a set of routines for interval arithmetic with extended 
precision using bfloat.

For instance, if one defines the sum  of intervals [a,b], [c,d] (with 0 
< a < b and 0 < c < d)  as
  Iplus([a,b],[c,d])=[a+c, b+d],
then I would define
 bIplus([a,b],[c,d]) = [bfloat(a)+bfloat(c), bfloat(b) + bfloat(d)]
etc.

 It seems that I have to put in 'bfloat' in every representation of a 
real number.

Is there a way to declare all variables to be evaluated using 'bfloat' 
without simply applying 'bfloat' to every occurrence?

TIA,
 -sen