I don't undertsand your explanation very well.
However, I think this would get you started.
Assumptions:
1. B2: The Account number to lookup are in the Summary Sheet
2. A1:C100 is the range to lookup on various sheets, where column A holds
the Account number and column C holds value you want.
3. Sheets to lookup : Sheet1, Sheet2, Sheet3, Sheet4.
4. The Account number to be looked up is on only one of the sheets e.g. if
value 108 is in sheet 2 and in sheet 4, the following formula will return
the value in the first sheet i.e. sheet 2.
=IF(COUNTIF(Sheet1!A1:A100,B2),VLOOKUP(B2,Sheet1!A1:C100,3),IF(COUNTIF(Sheet2!A1:A100,B2),VLOOKUP(B2,Sheet2!A1:C00,3,,0)
,IF(COUNTIF(Sheet3!A1:A100,B2),VLOOKUP(B2,Sheet3!A1:C100,2,0),IF(COUNTIF(Sheet4!A1:A100,B2),VLOOKUP(B2,Sheet4!A1:C100,2, 0),"not found in all sheet"))))
Referencing more than 7 sheets would be complicated (In Excel, 7 is the
maximum number of nested levels of functions - see the Excel help file).
You may consider a macro or using Pivot table