The Control Source defined in the image below represents:

$\backslash$table$[[$Property Sheet$],[$Selection type: Text Box$],[\backslash$table$[[$Text$3,$Text$3,],[$Format Data,Event,Other All$],[$Name$,$EndDateLabel,$],[$Label Name,$-[$StartDate$]$ & DurationDays$]-1,],[$Control Source,Short Date,$]]]]$

A Query

A Table

An Expression

A Form