Replace the " = " signe (equals) with the work " Like ".
Then write in the textbox something like "app*"
Note - remove the brackets from all the above.
The idea is that you must enclose the value itselft in brackets as I demonstrated. The = sign indicates equation (identity). The Like operator indicates the quite wide range of similarities including wildcards.
The filter string is written like a WHERE clause in a SQL statement (eg. ColumnName = Value AND ColumnName2 = Value2).
To make it easier for users, you may want to create a filter builder. You might have a ComboBox loaded with column names, another loaded with operators (=, >, <, <>, etc) and a TextBox for the value. The user selects a column, and operator, and types a value. They click an Add button and you build a filter string.
Let me know how it works...