This post on the MSDN forum:

http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=2064643&SiteID=1

…reminded me of something interesting I found out a few months ago. It seems that whereas you can’t mix regular and calculated measures in a set used in the SCOPE statement, you can rewrite the assignment to avoid using SCOPE and do a direct assignment instead. So, for example, if you were trying to assign to a regular measure and a calculated measure using a SCOPE statement like this:

SCOPE({[Measures].[RegularMeasure],[Measures].[CalculatedMeasure]});
    this=1;
END SCOPE;

You would get the following error:

A set has been encountered that cannot contain calculated members.
MdxScript(Cube1) (line, col) A set has been encountered that cannot contain calculated members.
The END SCOPE statement does not match the opening SCOPE statement.
MdxScript(Cube1) (line, col) The END SCOPE statement does not match the opening SCOPE statement.

You could rewrite the assignment as follows using two SCOPEs:

SCOPE([Measures].[RegularMeasure]);
    this=1;
END SCOPE;

SCOPE([Measures].[CalculatedMeasure]);
    this=1;
END SCOPE;

…but this is clearly a pain, as you’re duplicating your assignment logic. What you can do instead is this:

({[Measures].[RegularMeasure],[Measures].[CalculatedMeasure]})=1;

Not as easy to read as using SCOPE, I know, especially if you’re doing something complex, but at least it works! Now I wonder why SCOPE has this problem? Probably something worth opening an issue on Connect about…