Ssrs 2010 use fx button for inline sql

In an ssrs 2010 report, my dba wants me to change a stored procedure and place the sql into the report as inline sql. The problem is if I use the 'query designer' button, the sql is too long.
However if I use the FX button instead, the entire sql can be brought in. The window shows 'set expression for Query.CommandText'.
However the report does not know where the parameters to the report are. The 'refresh fields button'does not show the columns that are to appear in the dataset.

Thus can you tell me how to use the 'fx' button in this manner?

If this does not work, is there a way to make a long string of sql work in the ssrs 2010 report? If so, can you tell me how to accomplish this goal?

Why does the DBA not want a sproc?

I have to agree with @yosiasz - why does your DBA want you to use inline-SQL in a report where it cannot be modified (read: optimized) without redeploying the report?