I have a similar problem. I select values from a stored procedure like this

Select MANUMM,SUM(MENGE) as SOLL,...
from MatVergl(:AID)

but the report don´t display the field SOLL correctly. It seems the report
handles the field like it is a string. It don´t use the DisplayFormat and
the DBCalc objects can´t sum the values SOLL. I tried to change the TppField
settings (DataTyp,..) but I don´t get rid of this problem. The only solution
I found is to use a calculated fields SOLL_ like this
if AField.fieldname='SOLL_' then AField.asFloat:=ARow.byname('SOLL').asFloat;

I use RB6.03,IBOPipeline, TIB_Query