As far as we know, you can't use ActiveX control directly in SSRS. You can wrap Barcode ActiveX control into a Report Control with .Net language, if you are interested in writing a custom report control. Then you embed the wrapper control in SSRS.
A much simpler way is to use font products. See the links below:
HOWTO: Creating 2D Barcodes in Microsoft Reporting Service 2000 and 2005 (
http://mdn.morovia.com/kb/entry/10605/)
HOWTO: Adding Linear Barcodes in Microsoft Reporting Service 2000 and 2005 (
http://mdn.morovia.com/kb/entry/10606/)
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