This is kind of complicated.

In one sheet we have a rolling income statement (Jan-Dec) in which we enter
the figures for the actual month manually (this is the input sheet).

In second spreadsheet we have a similar rolling, but with budgets figures.

The third sheet only refers to the current month and it reads from both of
the sheets above; we only want to show the current month figures here.

For example if the current month is March, we want the third sheet to read
the figures corresponding to March from sheet one and the figures
corresponding to March from sheet two for the budget.

When I open sheet one to enter April figures, I want to see the numbers in
sheet two and sheet three change to the corresponding April figures without
copying cells.

What will be good here?