DateTimeDiff([firstdate],[laterdate],"days") will give you the number of days inbetween the first date and the later date.
If you divide by seven you'll know how many weeks occurred, and rounding up and multiplying by two should give the number of weekends if I'm thinking this through right (assuming the dates are all occurring on business days).
This ones a little tricky because for the first row in the Ticket, the elapsed is the difference between Submitted and Worked On and for the subsequent Status items, it the difference between the Worked on and the previous Worked on. When you add on the fact that you're looking for business days and not calendar days, it becomes a multi-step process.
This work flow gives you what you're looking for.
It generates a row for each of the dates between the start and end and then removes the weekends and holidays(must be considered if you're counting business days). Count the number of rows remaining and you have your answer.
Note that you may need to adjust the holiday list for your locale.