Date Validation In Conditional Splits

Hi All

I am trying to copy data from one table to another with a conditional split to validate the date.
In my source table, the date field open_date is stored as string YYYYMMDD (19941231) while in my
destination table it is stored as a datetime field.

My source date has bad data in the field, ie invalid dates e.g ( 20012017, 19701043).
I wanted to use a conditional Split to filter records with bad dates into a file
I was looking for a function like ISDATE (open_date) = True then go to table
else put in file. But have not been able to find one.

Or if they is another way to achieve this, I would be interested.

Thanks much in advance