Hi Amanda,
An approach you could take is to have a custom form attached to the tasks you want to measure this date difference on and have two calculated fields on that custom form.
The first calculated field would create a timestamp when the task was assigned to Team 123 and would look like this:
IF(Team ID = 'Insert ID of Team123 here',$$NOW)
The second calculated field would then work out the difference in weekdays between the task entry date and the date that the task was assigned to Team 123 and round the value to the nearest whole number. It would look like this:
ROUND(WEEKDAYDIFF(Entry Date,Insert name of first calculated field here),0)
After creating the first calculated field, don't forget to save the custom form and exit it before going back in to create the second field. This will ensure that the first field is committed to your databased so it can then be referenced in the second field.
Hope this helps.
Best Regards,
Rich.