Here's a possible solution. Your first field is where you select the date.
In the next field:
if (StartDate.rawValue==null) then
$.rawValue = ""
else
Num2Date(Date2Num(StartDate.formattedValue, DateFmt(2)) + 1, DateFmt(2))
endif
the next field:
if (StartDate.rawValue==null) then
$.rawValue = ""
else
Num2Date(Date2Num(StartDate.formattedValue, DateFmt(2)) + 3, DateFmt(2))
endif
the next field:
if (StartDate.rawValue==null) then
$.rawValue = ""
else
Num2Date(Date2Num(StartDate.formattedValue, DateFmt(2)) + 4, DateFmt(2))
endif
and so on.
Not pretty but it works. I can send you the sample if you'd like