SSIS reads nvarchar values as Null when Excel column includes decimal and string values

I have SQL Server 2012 SSIS. I have Excel source and OLE DB Destination.
I have problem with importing CustomerSales column.
CustomerSales values like 1000.00,2000.10,3000.30,NotAvailable.
So I have decimal values and nvarchar mixed in on Excel column. This is requirement for solution.

However SSIS reads only numeric values correctly and nvarchar values are set as Null. Why?

CREATE TABLE [dbo].[Import_CustomerSales](
 [CustomerId] [nvarchar](50) NULL,
 [CustomeName] [nvarchar](50) NULL,
 [CustomerSales] [nvarchar](50) NULL
) ON [PRIMARY]

Kenny_I