Hi
It is not possible to pull values from cross tab. You need to place price and date fields on detail section. Now find out minimum date and price i.e.
To find Minimum price.
Numbervar MinPrice;
If Minimum({table.date}) = {Table.date} Then {Table.Price}
MinPrice:={Table.Price}
To find latest price :
Numbervar MaxPrice;
If Maximum({table.date}) = {Table.date} Then {Table.Price}
MaxPrice:={Table.Price}
Now you can find the variance.