What is the rest of the script? What are the errors? Is this a script, or did you enter this manually in a Find?
if you entered it manually you should have entered just the date range, eg: 1/1/2010...31/12/2010
If it is part of a script it could have looked like:
Go To Layout (make sure it is on a layout from the LIDI Table)
Enter Find Mode
Set Field [ LIDI::Exam Date;(LIDI::Start Date & "..." & LIDI::End Date) ]
Perform Find (Untick the 'Restore Find Request')
Perhaps it's the set field step that's the problem. Many new users have trouble with it the first time around:
When Setting up Set Field, there are two Specify buttons that must be clicked. To get Set Field [Table::Field ; Expression], add set field to your script and click the first button (specify target field). Select Table::Field from the list of fields. Do not click the specify button next to the repetition box. Click OK to close this dialog box. Now click the lower specify button (calculated result) and create the expression to the right of the semicolon (;). Do not try to type in the semicolon.