Dynamic Function

I changed it to SP as suggested, but it is returning null, where as table has data pertaining to the date passed

ALTER PROCEDURE [p_Rec_cnt] 
                           (
                                        @InTableName NVARCHAR(100),
                                        @InDtColName NVARCHAR(50),
                                        @InDate NVARCHAR(50),
                                        @InRowCnt  INT OUTPUT
                           )
AS
BEGIN
DECLARE @vRowCnt NVARCHAR(50)
DECLARE @vTableName NVARCHAR(150)
DECLARE @vDtColName NVARCHAR(50)
DECLARE @vInDate NVARCHAR(50)
DECLARE @vSql NVARCHAR(500)
      SELECT @vTableName=@InTableName,@vDtColName=@InDtColName,@vInDate=@InDate
      SELECT @vInDate=''''+CAST(@InDate AS NVARCHAR)+''''
      SELECT @vSql='SELECT '+@vRowCnt+' = COUNT(*) FROM '+@vTableName+' WHERE '+@vDtColName+'='+@vInDate
      EXECUTE SP_EXECUTESQL @vSql, N'@vRowCnt NVARCHAR(50) OUTPUT', @vRowCnt OUTPUT
      SELECT  @InRowCnt = @vRowCnt
END

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Neil