I found the answer on another post. The original post was answered by
Magus069 and for those looking for this answer I'll share below.The date
field which you want it to be readOnly will need to have the following
FormCalc script within the calculate eventif (DateTimeField1.rawValue <>
null) then Num2Date(Date2Num(DateTimeField1.rawValue,"YYYY-MM-DD") + 2,
"YYYY-MM-DD")else nullendif