Have you considered testing a substirng of the formatted value of the DateTime1 field for "Saturday"?
if (DateTimeField1.rawValue ne null) then
if (Substr(DateTimeField1.formattedValue, 1, 08) eq "Saturday") then
Num2Date(Date2Num(DateTimeField1.formattedValue, "EEEE, MMM D, YYYY")+ 2, "EEEE, MMM D, YYYY")
else
Num2Date(Date2Num(DateTimeField1.formattedValue, "EEEE, MMM D, YYYY")+ 1, "EEEE, MMM D, YYYY")
endif
else
""
endif