i was looking for a formula that shows both of the following depending on the cell value:

• need it to determine days between cells that have invoice date and ship date populated;
• need it to determine days between cells that have invoice date and no ship date (rolling)
• need it to understand that if ship date is populated, that it takes precedence over no ship date
• I need it be able to stop the day count if the ship date is populated
• I need it to be able keep going with count if ship date is not populated.

attachment is a sample of what I have