How To Add Variable To Sql Command Text Field

In the data flow task I have multiple OLE DB source task to retreive data from a cube using MDX. Below is an example of the query from sql command text field: I have a few questions on how to modify this statment to make it more robust.

1) The where clause [Calendar].[Quarter 2 (2007)] should actually be some kind of variable that will change each time
the user runs this project. So I am wondering how to make this a variable and get it into this field.

2) I had thought that I could use the SSIS variable. I have created one, but I can not figure how to get it into the field that
contains the given select statment.

3) I believe that once I get this variable part to work then I want a way to have user set this data value. Either by selecting data from a table in database or through a user interface where user enters data. I did do some resarch on creating a user interface, but I did not understand what I had to do, so if any one knows where to find a tutorial on how to do this let me know, or what they believe the best/easiest way is to get data from user to fill this where clause.
select * from OPENROWSET('MSOLAP', 'DATASOURCE=local; Initial Catalog=Patient Demographics 2005;',
'with member [Measures].[TimeDisplayName] as [Calendar].CurrentMember.Name
SELECT NON EMPTY { [Measures].[TimeDisplayName],[Measures].[Adjusted Relative Weight],[Measures].[Adjusted Case Weight]} ON COLUMNS,
({[Facility].[REGION].[NATCODE], [Facility].[REGION].[REGCODE]} *
[RIC].[CMGGRPCD].ALLMEMBERS) ON ROWS FROM [ESR]
WHERE [Calendar].[Quarter 2 (2007)]
')