how to retrieve values from a multiple select text box prompt

Hi,
I am using a multi-select text prompt, so that I can enter multiple values. I am unable to filter the data from this prompt ( lets say separated by commas ) via a query , so that I can get the results and show only the values that are contained in the text box.
Also what adds to the complexity is that when the user enters the data in the prompt, the results should have all records that contain those values e.g ( %value1%, %value2%, %value3% ) , not exact values, but data that contains these words.

We are bringing data from RTC into Insight and running reports from Insight. The report has a Text Prompt for entering tag values to 'include or exclude'.

For example there are 2 workitems in RTC.
workitem1 has  |tag1|tag2|tag3| in the 'Tags' field
workitem2 has  |tag4|tag5|tag6|tag7| in the 'Tags' field.

When we run the report and enter tag1 in the text prompt, it should pull up workitem1
when we enter tag1,tag6 as input to the text prompt, it should pull up both workitems - workitem1 and workitem2.

I hope this example makes it clearer. If someone knows how to construct the right filter to pull up this data, it would be very helpful.

Can someone shed more light on this ?
Thanks