I would probably investigate using an Activity Start Rule.  Start Rules are ways to instruct K2 when to begin the activity.  Attached is an example screen shot to explain how to approach this:

1. Create an Activity (called 'Check External Data' in below)

2. Add an event (perhaps server event) that does the lookup (the green area of the screenshot).  This should update something like a process data field

3. Create some lines coming out of this activity.  One to the next activity and one that loops back (blue area of screenshot) onto this activity.  The line rules should have logic that checks the data field set in the activity.  if it is false, it loops back, if true, then moves to next activity.

4. set a Start Rule on the Check External Data activity for 10 minutes (red area of screenshot)

So at run time, the activity 'Check External Data' will be hit, then K2 will wait 10 minutes before executing.  It will then hit the 'Call DB' activity and check the DB and look for that value.  If it finds it, it will set the datafield (ExternalValue) to true, then the line to the next activity will be followed.  If it doesn't find the value in the DB, then the loopback line will be followed at which point the cycle will repeat (wait 10 minutes...)

HTH.

I will try to implement this today.

Thanks a lot.