add a calculated column

Hi,

I need help with the implementation of a new column. In this column, the realized sales must be subtracted from the planned sales (from the past quarters and current quarter) and distributed to the following quarters.

Examples:

Planning in the first quarter:

the sales in the first year are 96.550€. The difference between the realized and planned sales is 3.450€. The 3.450€ are distributed on the planned sales of the next quarters. (1.150€ are added to the planned values of the next quarters.)

when we are in the second quarter the planning should look like this:

3450€ are missing from the first quarter. the difference between realized and planned sales from the second quarter are -1900€ (100.000€- 101.900€= -1.900), so 1900€ more were achieved than planned. The difference between realized and planned sales from Q1 and Q2 is 1550€ (realized sales: 3450€+(-1900€) = 1550€). 1550€ must be distributed over quarters 3 and 4

Thanks!