Ananthram
Vlookup, as with all functions, updates automatically every time the data is changed
This occurs unless
1. Calculation is set to Manual instead of Automatic,
goto the Formulas, Calculation Tab and set Calculation to Automatic
2. The data range changes and is now larger than the Vlookup Formula is using
To fix this use what is called Dynamic Ranges
So instead of using:
=Vlookup(A1, B1:C10, 2, False)
Try:
=VLOOKUP(A1,OFFSET(B1:C1,,,COUNTA(B1:B200)),2,FALSE)
Adjust ranges to suit