If I understand what you are asking, you want to have a parameter that allows you to search by only a portion of a value, as opposed to entering a full value.
1. Create a parameter (this will be your search box)
2. Right click on the Data set under Report Data on the left side of BIDS and select Dataset Properties.
3. Choose Parameters
4. Edit the Parameter value (this is your search box) by click on the fx on the right side.
5. Enter ="%" & Parameters!YourParam.Value & "%" replacing "YourParam" with the actual parameter name.
6. In the Query Designer add LIKE @YourParam to the filter for the column you are looking to search in.
If I misunderstood what you have asked, my apologies. :-)