Help creating a visual shipment tracker in tableau 8.2

Hi All,

I was wondering if someone could help me sort through some of the issues I am having with this dashboard concept.

The sheet needs to show how far along the shipments are by using [Days Intransit] added to the [Intransit Ship Date] which would then be displayed as a box shape (to mimic a parcel) in between the start and end dates in order to give a visual indicator of when the parcel is arriving, each row would be differentiated by the [Shipment Number].

My Data has:

[Intransit Ship Date] ex: 9/29/16

[Days Intransit] ex: 40

[Intransit ETA Date] ex: 12/1/16

[Shipment Number] ex: 1234567

I think I need to create a calculated field to show [Intransit Progress Date], But this is all I can figure and it did not work "DATEADD('day',[Days Intransit],[Intran Shp Dt])".  Tableau doesn't like [Days Intransit] in that position, instead wanting a fixed number.

Any ideas? much appreciated!

**bonus points if the solution colors the parcel if the ETA is surpassed by days intransit + ship date** (this happens )