Date comparision

Hi All,

I want to comparision two dates..

I have Invoice Date and LR date..i want that LR Date must not be less than Invoice Date...what should be condition for it..

Ex:-

Invoice Date - 15.04.2008 ......LR Date 20.04.2008 - Correct

Invoice Date - 15.04.2008 ......LR Date 10.04.2008 - Wrong (should not taken).

Plz tell me coding part..

Thanks..