crystal report subtotals by page

You need to use three formulae

Formula 1 : @Reset
NumberVar x;
WhilePrintingRecords;
x:=0;

Formula 2 : @Sum
NumberVar x;
WhilePrintingRecords;
x:=x+{DatabaseFiled};

Formula 3 : @Display
NumberVar x;
WhilePrintingRecords;
x

Place Formula1 in Page Header and suppress
Place Formula2 in Details section and suppress
Place Formula3 in Page Footer and Dont suppress