Crystal Shared variable

Hey all;

I have a formula set up that checks if a date from the database is between a certain range - IE between 1st April 2007 and 31st March 2008.

However, at the end of that period - 31st March 2008, I'll need to change this range to 1st April 2008 - 31st March 2009. This formula is repeated for several entries.

I'm fairly new to Crystal, so I was just wondering if there was any way I could declare and populate just two strings in one place, and then refer to these strings in the rest of the formulas, eg:

vb Code:

Public StringFrom as string
Public StringTo as string
 
StringFrom = "01/04/2007"
StringTo = "31/03/2008"
 
 
'   If Date of CP12 falls after 1st of April 2007
if DateDiff("y", StringFrom, {data.cp12 date}) > 0 then
'   If Date of CP12 falls before 31st March 2008
if datediff("y", StringTo, {data.cp12 date}) < 0 then
'   tally it up
formula = 1
else
end if
else
formula = 0
end if

I've tried that, but Crystal says that "a date is required here".

Help? :(