I have just taken on a workbook with many work sheets that all contain a very large number of VLOOKUP formulas containing IFISERROR in order to ensure there are no errors reported which will prevent the many calcuations from working correctly.

My issue is that the sheets contain many areas (forms) for input by the users and relies upon immediate update of information to be able to make various decisions and try multiple "what if" scenarios on the numbers, however the calculation of the workbook takes over three minutes and is really spoiling the "useability" of the tool the workbook is supposed to provide.

Is there an alternative to IFISERROR that will provide the same functionality but be less demanding when re-calculating?