- If Target resolution date and Actual Resolution Date is blank, calculate the number of business days between Date Identified and today's date
- If Actual Resolution Date is blank, calculate the number of business days between Date Identified and today's date
If Actual Resolution Date is not blank, calculate the number of business days between Date Identified and Actual Resolution Date
Try this:
IF(
isnull([Target resolution date]) and isnull([Actual Resolution Date]), weekdaysub(Today(), [Date Identified]),
isnull([Actual Resolution Date]), weekdaysub(today(), [date Identified]),
not isnull([actual resolution date]), weekdaysub([actual resolution date],[date identified]))