Trying to use Substring is the first part of a SelectFrom Where clause

Sorry for posting so many questions lately.  

in my command, I want to get the first two characters of the screen ID. If it is SM, I want to exclude the record from the selection.

 cmd = new SelectFrom<UploadFileRevision>

       .InnerJoin<UploadFile>.On<UploadFile.fileID.IsEqual<UploadFileRevision.fileID>>

       .InnerJoin<ICSUploadFileView>.On<ICSUploadFileView.fileID.IsEqual<UploadFile.fileID>>

       .LeftJoin<ICSSystemFiles>.On<ICSSystemFiles.systemFileName.IsEqual<UploadFile.name>>

     .Where<UploadFile.primaryScreenID.IsNotNull.And<ICSSystemFiles.systemFileName.IsNull>

     .And<Substring<UploadFile.primaryScreenID, int0, int2>.IsNotEqual<SMScreenConstant>>>

     .View(this);

I know Substring can be used in the predicate, but do you know of a way to do it in the subject of the Where?

I am using a SQL View since you can do a field not in ("SM") in the where in SQL. I want to get rid of the need for a SQL View if possible.