That's bizarre, what does the 24 and null mean?
Anyway, try:
stringvar MyDateStr:= {table.field};
datetimevar MyDate;
MyDate:= cdatetime(val(mid(MyDateStr,1,4)),val(mid(MyDateStr,6,2)),val(mid(MyDateStr,9,2))
,val(mid(MyDateStr,12,2)),val(mid(MyDateStr,15,2)),val(mid(MyDateStr,18,2)));
MyDate
Replace {table.field} with your datetime string field.
-k