Count workday between datetimepicker?

Question

Hi, i have problem when counting between datetimepicker



here is the data on database


PROJECT
========
START_DATE
END_DATE
TOTAL_DAY




and I have 2 Datetimepicker on VB.NET


Datetimepicker1  ---> contains START_DATE
Datetimepicker2  ---> contains END_DATE
txtTotal            ---> will be automatically generated once both Datetimepicker are selected and contains formula END_DATE - START_DATE, the result will be added to TOTAL_DAY in database


how to calculate it on VB.NET only for workdays, Saturday and Sunday doesn't need to count.








any helps would be appreciated, thx in advance :)