Required difference between two dates/times in hours

Hi,

I am using the following formula for getting difference between two dates/times in hours.

=(NETWORKDAYS(A1,B1,)-1)*9+IF(NETWORKDAYS(B1,B1),MEDIAN(MOD(B1,1)*24,17, 8),17)-IF(NETWORKDAYS(A1,A1),MEDIAN(MOD(A1,1)*24,17,8),8).

Need some following changes in the above below formula

1. From the above formula if i want to one holiday then how to calculate.
2. From the above formula result is coming like 0.75 (actual time is 45mins) insted of this can we get the reslut in time fomula like 00:45 or 1:20(1 hr 20mins).

Please help on this.

Regards
Kasi