Calendar and weekend days, rates calculations? Very challenging

Please see attached I am not far off finishing this but I have had a couple of problems -

NEEDS TO POPULATE E27 AS 288 SAT AND SUNDAY HAVE A DAILY RATE OF 24
ANOTHER ISSUE IS IF WE HIRE A MACHINE FROM 01/07/2012 TO THE 02/07/2012 THIS COUNTS TWO WEEKENDS IT SHOULD ONLY BE ONE
I ALSO TRIED - "=ROUNDUP((E23-NETWORKDAYS(E21,E22))/2,0)" BUT THAT MEANT IT DIDNJT WORK FROM 01/07/2012 TO 07/06/2012