I need to calculate the total WORK-hours (08:00-17:00) between two
date/time-stamps;
-excluding WEEKENDS
-excluding PUBLIC HOLIDAYS

eg#1.: A1=START DATE/TIME & A2=END DATE/TIME & A3=RESULT ([hh]:mm)
A1 11-01-2008 09:00:00
A2 11-01-2008 11:00:00
A3 02:00

eg#2.: A1=START DATE/TIME & A2=END DATE/TIME & A3=RESULT ([hh]:mm)
A1 11-01-2008 09:00:00
A2 14-01-2008 11:00:00
A3 11:00

eg#3.: A1=START DATE/TIME & A2=END DATE/TIME & A3=RESULT ([hh]:mm)
A1 14-01-2008 09:00:00
A2 16-01-2008 11:00:00
A3 20:00