Validation
The Validation tab is used to type verifying formulas which can test the validity of records. The feature only works when you enable the formula.
If the returned value is false, the record is considered invalid.
The algorithm above verifies if the EndTime comes after the StartTime.
In the case of the screenshot, if the value turns out to be false, a warning message will come up signing an existing error in the EndTime entry.
It is important to note that within a formula, the value of an entry of an actual record can be reached through the name of the entry.
Result:=Entryname+3;
If you want to set a constant value for the entry, then instead of
Entryname:=3;
you have to use the SetValue function from the list of functions in the formula editor:
SetValue(Entryname, 3);.