Formula problem, sometimes don't add the value

Question

Hi everybody,
I'm trying to learn manage this tool (crystal report) I use visual basic 2005 with the crystal for visual basic. Actually I've a problem with some formula fields. My report has several summarize columns (I sum the values) , not all the columns have values so not all the result fields has values. The problem becomes because I have to sum the result fields, and if i do a formula with this:
+ {@horasTinsitu} + {@ConvertirEnSegundosTreal} + {@ConvertirEnSegundosTtaller}
But only works if the three formulas has values, if one formula is empty the result looks empty, I think the problem was in the value of the formulas and I tried to evaluate with u201Cisnullu201D but neither.
Please, somebody has an idea.
Thanks everybody
Well my English it's bad but I think it's possible understand it.

Answer 1

I finally do it, this is the code
local numbervar InSitu;
local numbervar Remote;
local numbervar Taller;
local numbervar Phone;
if isnull({@T_insitu}) then  //{@T_insitu} is the formula to summarize details and add their values...
    InSitu:= 0
else
    InSitu:= {@T_insitu};
if isnull({@T_remoto}) then
    Remote:= 0
else
    Remote:={@T_remoto} ;
if isnull({@T_taller}) then
    Taller:= 0
else
    Taller:= {@T_taller};
if isnull({@T_telefono}) then
    Phone:= 0
else
    Phone:={@T_telefono} ;
InSituRemoteTallerPhone;
Now looks easy but it's very diferent of the visual code I usually do.
well  THANK YOU VERY MUCH EVERY BODY...
Dani