Reformatting date field

Hello

I am receiving files from the customer with the inconsistent format of date fields

most of the time it is yyyy-mm-dd
But sometimes it is yyyy/mm/dd

I am trying to use the following calculations to correct the issue but it does not work.

IF SubString([INVOICE DATE],3,1)='/' then Result := RightString([INVOICE DATE],4)+'-'+SubString([INVOICE DATE],4,2)+'-'+LeftString([INVOICE DATE],2) else Result : =[INVOICE DATE]

This one works

begin
if SubString([INVOICE DATE],3,1)='/' then
Result := RightString([INVOICE DATE],4)+'-'+SubString([INVOICE DATE],4,2)+'-'+LeftString([INVOICE DATE],2)
else
Result :=[INVOICE DATE];
end;