Exicse dealer quaterly return.

simply follow the 23D register maintained 

dealer return is nothing but abstract of the 23D register 

my question is which value should be entered in the purchase details.

a.) net amount of cenvat credit utilised or

b.) actual value of bill each time.

purchase details are fixed, they should be as per the purchase invoice issued by manufacturer, ( in case you are 2nd stage dealer, 1st stage dealer has shown the assessable value and duty payment by manufacturer ) how ever sale price of yours will be entered in part A, but the duty per unit will remain same as per the purchase invoice, 

Only that invoice (total invoice qty and total excise duty) against which you have passed the Cenvat Credit in that period, will be shown.