Does anyone know how to do current date as a default parameter?

I tried :

this formula
DateVar StartDate;
If {?Thru Date} = Date('1/1/1900') then
(
  StartDate := DateAdd('m', -1, CurrentDate);
  StartDate := Date(Year(StartDate), Month(StartDate), 1);
)
else
  StartDate := {?Thru Date};
StartDate


but getting a date is required error on the DateAdd ??

Any ideas would be great

Thanks
Joe

Thanks

That formula works now..
But unlike SSRS why can't I put today's date in the default value in the parameter?

I use 1/1/1900 in the default which gives me today's data, but if someone what's to use yesterday, they have to manipulate the calender from 1900...