Check date range

["derek gonsalves" <d_gons@xxxxxxxxxxx>]

Hello everyone,

Is there any Op-code for date Range?
I have a date field which is 7,0 in length - 1072207 
(Century/month/day/year)
The requirement is as follows -
I need to enter a rate for a particular period for a product.

     Perid
> From           To             Product
07//16/07    08/16/07   ABC

Now i need to perform validations to make sure that the next date range 
entry for that product does not exist.

Thus -
07/23/07  to  08/23/07 should not be allowed , since we already have a rate 
for that product in that  period(rate for the same product should be allowed 
as long as they reference disjoint periods)

Is there any opcode which i can use for checking the range OR any other 
suggestion?

Thanks in advance
Derek