Search A String...

I'm trying to create a query that searches the string in a field, for a substring that the user specifies when the query is run. This is the SQL code:

SELECT tblStatement.Date, tblStatement.[Payment Type], tblStatement.Details, tblStatement.[Paid Out], tblStatement.[Paid In]
FROM tblStatement
WHERE (((tblStatement.Details) Like "**"))
ORDER BY tblStatement.Date;

between those two asterixes on the WHERE line, I'd like a string that the user has been prompted for. I've tried this:

WHERE (((tblStatement.Details) Like "*[Enter a String]*"))

But that fails to work, I guess because its in quotations. If I simply had Like [Enter a String], then I get the prompt, but I'll need to enter a string which exactly matches what I am looking for. In other words, I need a query which will search say, "abcdefg" for the user defined input: "abc", which will return that result. I just dont know how to get this to work :s