HI

I have a rather complex problem that might take a little explaining.

Basicaly, im designing a workbook that logs instances on accidents. Its devided into four seperate spreadsheets;

Function (where you choose which financial period you wish to view)
Periodical Report (where the data is made avalable as a report)
Weekly Input ( the current years log, which the report takes information from)
previous year (the last years log)

The problem im having is with my formula when on the cusp of the year. Our financial periods are 1-13. In the periodical report, it displays the CURRENT PERIOD, along with the 3 periods PRIOR to the current. However, I cant get my spreadsheet to recognise when it needs to take information from the PAST or PRESENT year. For example, if im viewing period 1 in the current year, it also needs to show periods 13, 12, 11 from the past year. though if i was using period 13 in the current year, it would need to display periods 12, 11, 10 also from the current year. My formula currently is as follows


=CONCATENATE(IF(D$4=1,'Weekly Input (Current Year)'!BC8,""),IF(D$4=2,'Weekly Input (Current Year)'!BD8,""),IF(D$4=3,'Weekly Input (Current Year)'!BE8,""),IF(D$4=4,'Weekly Input (Current Year)'!BF8,""),IF(D$4=5,'Weekly Input (Current Year)'!BG8,""),IF(D$4=6,'Weekly Input (Current Year)'!BH8,""),IF(D$4=7,'Weekly Input (Current Year)'!BI8,""),IF(D$4=8,'Weekly Input (Current Year)'!BJ8,""),IF(D$4=9,'Weekly Input (Current Year)'!BK8,""),IF(D$4=10,'Weekly Input (Current Year)'!BL8,""),IF(D$4=11,'Previous Year'!BM8,""),IF(D$4=12,'Previous Year'!BN8,""),IF(D$4=13,'Previous Year'!BO8,""))

however this does not surfice. As it cannot discriminate between periods in the last year and the present year.

as you can see its a bit of a mind-bender, hope someone can help me out because im going slowly insane

Ben