Help with formatting for Cross Tab Report Crystal 2008

Question

This is probably a simple question.  I have a cross tab report that displays sales by month for a period of 6 months.  These sales columns are formatted to be numbers with no decimals.  In addition to these columns, I have inserted columns that display the percentage up/down in sales over the previous month.  If I try to format the percentage columns, it changes every column to then display "##,##.##%" when I need to keep the sales columns at "##,###" with no decimal or percentage sign.
1.  Is there a way to change the formatting of some of the columns but not all in a cross tab report?
2.  If not, can I add a function that would change these in the calculation formula of the calculated member? 
I tried to add "%" but it wants it to return a number.
Here is the current code:
//The calculation formula is used in place of the summaries in Calculated Members.
// This calculation formula must return a/an Number value.
If GridValueAt (CurrentRowIndex,CurrentColumnIndex-3,CurrentSummaryIndex) = 0 then 0 else
((GridValueAt (CurrentRowIndex,CurrentColumnIndex-1,CurrentSummaryIndex) -
GridValueAt (CurrentRowIndex,CurrentColumnIndex-3,CurrentSummaryIndex)) /
GridValueAt (CurrentRowIndex,CurrentColumnIndex-3,CurrentSummaryIndex)) * 100
Any help is appreciated. 
Thank you,
Tobi

Answer 1

Carl,
Thank you for your help.  I did try your method but still couldn't get it to ignore the fact that it wanted a number.  I changed my approach a litte and managed to solve the problem.  Here is the method that I chose which managed to solve the problem.  If this is a poor way to solve it, please let me know as I am always open for new ways.
Format Field > Number Tab > Customize > Currency  Symbol Tab
Checked Enable Currency Symbol Fixed, changed  currency symbol to %.  This is the same thing that I did before which changes it for all columns. 
Beside Enable Currency checkbox, I added this formula:
// This conditional formatting formula must return one of the following Currency Symbol Constants:
// crNoCurrencySymbol
// crFixedCurrencySymbol
// crFloatingCurrencySymbol
If GridRowColumnValue("InvoiceLine.TxnDate") = Date(0,0,0) then
    crFixedCurrencySymbol  
else
    crNoCurrencySymbol
My added columns have a null date field so they take the currency format.  My other columns do not so they do not take the formatting.
Thanks again for the help.
Tobi
Edited by: Tobi@TABeverage on Dec 2, 2009 3:58 PM