Check the Qlikview Help for this.
A field may be flagged as an input field by listing it in an inputfield statement before it is referenced in any load or select statements.
Input fields behave somewhat differently from regular fields. The most important difference is their ability to accept changes in field values, interactively or programmatically, without running the script. Field values must be loaded into the field via load or select statements. Each field value loaded in the script will create a placeholder for a field value replacement value. Only existing field values can thus be changed interactively or programmatically. The replacement value is user dependent, i.e. when an input field is used on a server, different users will see different sets of input field values
In input fields all field values will be treated as distinct, regardless if several have the same value.
The syntax is:
fieldlist is a comma separated list of the fields that should be flagged as input fields. The wildcard characters * and ? are allowed in field names. Quoting of field names may be necessary when wildcards are used.