You can use the "Find/Replace" menu item from the Edit menu. Enter the search text and click the "All records" and "All fields"
This can be done using a script and a loop, but you will need to make sure that all the fields you want to search on, and only the field you want to search on, are in the layouts tab order. So you might want to setup a separate layout to perform the search, but the user will not notice any change.
Once you have set all the field in the tab order you need to set up the script to perform the search, I will assume for this that the field the user inputs the search criteria into is called gSearchField, and is set to be a global.
The script will go like this:
Set Error Capture [On]
Set Variable [ $SearchCriteria; TABLE::gSearchField ]
Go to Layout [ “SearchLayout” ]
Enter Find Mode [ ] // Deselect 'Pause'
Set Variable [ $StartingField; Value:Get ( ActiveFieldName ) ]
Go to Next Field
Set Field [ $SearchCriteria ]
Exit Loop If [ Get ( ActiveFieldName ) = $StartingField ]
Perform Find [ ]
Go to Layout [ “OriginalLayout” ]
#// Check result and if no records found alert user.
If [ Get ( FoundCount ) = 0 ]
Show Custom Dialog ["Message" ; "No Records Found."]
Enter Browse Mode 
And then you run this after the user inputs a search criteria in the gloabal.
Let me know if anything is unclear and I will expand upon it for you.