calculate a complex field

[nafise]

Hi,
I have a problem in calculating a field in a table.
I have 2 tables with these fields:
1- examcode , p1, p2, P
2- examcode, f1, f2

I want to update the first table to calculate the value of "P" field. It is a bit complex, because I want it to be calculated like :
P= (p1 * f1 + p2 * f2) / (f1 + f2) if p1 <> -1 and p2 <> -1 ( if any of these two is -1 it should be omitted from the formula) (p1 , f1 and p2, f2 are the correspond fields from the two tables )
(off course there are other fields in these tables and I can't put them in one table)

I'll be glad if anyone could help me,
thanks

[epots9]

Hi,
I have a problem in calculating a field in a table.
I have 2 tables with these fields:
1- examcode , p1, p2, P
2- examcode, f1, f2

I want to update the first table to calculate the value of "P" field. It is a bit complex, because I want it to be calculated like :
P= (p1 * f1 + p2 * f2) / (f1 + f2) if p1 <> -1 and p2 <> -1 ( if any of these two is -1 it should be omitted from the formula) (p1 , f1 and p2, f2 are the correspond fields from the two tables )
(off course there are other fields in these tables and I can't put them in one table)

I'll be glad if anyone could help me,
thanks

lets get this straight,first you:

get the data p1, p2, f1, f2 from the database
check to make sure that p1 and/or p2 doesn't equal -1
if they do
???
if they don't
P= (p1 * f1 + p2 * f2) / (f1 + f2)
then update the table field

is this correct?