Where Clause Problem When Passing In Data Dynamicly - HELP!

I have a stored proc that I am trying to use for sorting and paging below is a portion of it. When I hard code "Stan" into the Where clause I get all the records back that where posted by "Stan" but when I try to pass in "Stan" as a variable it tells me something about an invalid column name.

Here is the working version. When I hard code "Stan" into the Where Clause it works. I am using 2 single quotes on each side. See Where clause.

SET @sql ='SELECT [ThreadName],[PostID],[PostTypeID],[LanguageID],[PostAccessID],[UserID],[ThreadID],[PostParentID],[VoteSummaryID],

[Subject],[Body],[PostAuthor],[PostDate],[IsApproved],[TotalViews],[FormattedBody],[IPAddress],[PostCount],[ArticleCount],

[TrackbackCount],[IsSticky],[StickyDate]

FROM

(SELECT t.[ThreadName], p.[PostID],p.[PostTypeID],p.[LanguageID],p.[PostAccessID],p.[UserID],p.[ThreadID],p.[PostParentID],p.[VoteSummaryID],

p.[Subject],p.[Body],p.[PostAuthor],p.[PostDate],p.[IsApproved],p.[TotalViews],p.[FormattedBody],p.[IPAddress],p.[PostCount],p.[ArticleCount],

p.[TrackbackCount],p.[IsSticky],p.[StickyDate],ROW_NUMBER() OVER(ORDER BY ' + @sortExpression + ') as RowNum

FROM syl_Posts p

INNER JOIN syl_Threads t ON t.[ThreadID] = p.[ThreadID]

WHERE t.[PostAuthor] = ''Stan'')



AS syl_TPInfo

WHERE RowNum BETWEEN ' + CONVERT(nvarchar(10), @startRowIndex) +

' AND (' + CONVERT(nvarchar(10), @startRowIndex) + ' + '

+ CONVERT(nvarchar(10), @maximumRows) + ') - 1'


Not working when I try to pass in a variable into the Where clause.

SET @sql ='SELECT [ThreadName],[PostID],[PostTypeID],[LanguageID],[PostAccessID],[UserID],[ThreadID],[PostParentID],[VoteSummaryID],

[Subject],[Body],[PostAuthor],[PostDate],[IsApproved],[TotalViews],[FormattedBody],[IPAddress],[PostCount],[ArticleCount],

[TrackbackCount],[IsSticky],[StickyDate]

FROM

(SELECT t.[ThreadName], p.[PostID],p.[PostTypeID],p.[LanguageID],p.[PostAccessID],p.[UserID],p.[ThreadID],p.[PostParentID],p.[VoteSummaryID],

p.[Subject],p.[Body],p.[PostAuthor],p.[PostDate],p.[IsApproved],p.[TotalViews],p.[FormattedBody],p.[IPAddress],p.[PostCount],p.[ArticleCount],

p.[TrackbackCount],p.[IsSticky],p.[StickyDate],ROW_NUMBER() OVER(ORDER BY ' + @sortExpression + ') as RowNum

FROM syl_Posts p

INNER JOIN syl_Threads t ON t.[ThreadID] = p.[ThreadID]

WHERE t.[PostAuthor] = ' + @PostAuthor + ')



AS syl_TPInfo

WHERE RowNum BETWEEN ' + CONVERT(nvarchar(10), @startRowIndex) +

' AND (' + CONVERT(nvarchar(10), @startRowIndex) + ' + '

+ CONVERT(nvarchar(10), @maximumRows) + ') - 1'