Hi,
this isn't complicated to realize:
Just add a small FormCalc script into the possible oldest date field exit event.
In this example the font color of the Datefield2 will change to red if the selected date is before August the 1st 2014.
var dateFormat = "MM/DD/YYYY"
if (Date2Num($.formattedValue, dateFormat) lt Date2Num("08/01/2014", dateFormat) ) then
DateField2.font.fill.color.value = "255,0,0"
DateField2.caption.font.fill.color.value = "0,0,0"
else
DateField2.font.fill.color.value = "0,0,0"
DateField2.caption.font.fill.color.value = "0,0,0"
endif