Using a formula result of current month in other formula of future months

Hello Gurus,

I have very simple calcalution to perform but I'm not sure how to achieve it.

Let me try to explain:

I have the following query:

Time(Months) in collumns.

Keyfigures /Formulas in rows.

Below table shows the result I want to achieve

         06.2008   07.2008   08.2008   09.2009  10.2009   11.2009
KF1        50        60        70        80        90        95
KF2        30        30        40        30        50        40
F1         ..        ..        30        ..        ..        ..
F2                             70        60        80        70

For the current month (in this case 08.2009) query calculates the difference of KF1 - K2 into formula field F1. This difference F1 shall now be added in current and all future months (09.2009, 10.2009, ...) to KF1 and output to F2 (F2 = KF2 + F1). Above table shows how it should look like. What I get is the following:

         06.2008   07.2008   08.2008   09.2009  10.2009   11.2009
KF1        50        60        70        80        90        95
KF2        30        30        40        30        50        40
F1         ..        ..        30        ..        ..        ..
F2                             70        30        50        40

F2 calculation works for the current month but problem is that the result of F1 in 08.2008 (30 = 70 - 40) is not available in the future months.

Is there any way to solve this within a query?