Release 10.1A: OpenEdge Development:
ADM Reference

QueryString

Pending query string to use in the next openQuery. This value is updated on the client by query manipulation functions.

Data type: CHARACTER

Notes:

Read and Write.
This property should not be changed by code but is useful for debugging code.
The method always returns a WHERE clause. If the QueryString property has not been set, it uses the current WHERE clause - QueryWhere. If there is no current use the design where clause - OpenQuery.
The openQuery calls prepareQuery with this property.