SETRANGE

void SETRANGE(string FieldName, 
  object FromValue = null, 
  object ToValue = null);

Use this function to set a filter.

Customer:SETRANGE('Code','10000');

Sets a filter to value 10000

Customer:SETRANGE('Code','10000','20000');

Sets a filter from 10000 to 20000

Customer:SETRANGE('Code');

Clears filter in field Code.