I think this may do what you want?

SELECTCOUNT(*) OVER (PARTITION BY _bvSerialMasterFull.SerialNumber) AS SerialCount,

_bvSerialMasterFull.SerialNumber, _bvSerialMasterFull.SNStockLink, _bvSerialMasterFull.SNDateLMove, _bvSerialMasterFull.CurrentLoc,

_bvSerialMasterFull.CurrentAccLink, _bvSerialMasterFull.StockCode, _bvSerialMasterFull.CurrentAccount, _bvSerialMasterFull.CurrentLocationDesc,

_bvSerialNumbersFull.SNTxDate, _bvSerialNumbersFull.SNTxReference, _bvSerialNumbersFull.SNTrCodeID, _bvSerialNumbersFull.SNTransType,

_bvSerialNumbersFull.SNWarehouseID, _bvSerialNumbersFull.TransAccount, _bvSerialNumbersFull.TransTypeDesc,

_bvSerialNumbersFull.SerialNumber AS Expr1, _bvSerialNumbersFull.SNStockLink AS Expr2, _bvSerialNumbersFull.WarehouseCode,

_bvSerialNumbersFull.TrCode, _bvSerialNumbersFull.CurrentLocationDesc AS Expr3, _bvSerialNumbersFull.CurrentAccount AS Expr5,

WhseMst.Name, _btblInvoiceLineSN.cSerialNumber, _btblInvoiceLines.fUnitPriceExcl, StkItem.Code, StkItem.AveUCst, StkItem.ItemGroup

FROM _btblInvoiceLineSN INNER JOIN

_btblInvoiceLines ON _btblInvoiceLineSN.iSerialInvoiceLineID = _btblInvoiceLines.idInvoiceLines INNER JOIN

_bvSerialMasterFull INNER JOIN

_bvSerialNumbersFull ON _bvSerialMasterFull.SerialCounter = _bvSerialNumbersFull.SNLink INNER JOIN

WhseMst ON _bvSerialNumbersFull.SNWarehouseID = WhseMst.WhseLink ON

_btblInvoiceLines.iStockCodeID = _bvSerialMasterFull.SNStockLink AND

_btblInvoiceLineSN.cSerialNumber = _bvSerialMasterFull.SerialNumber INNER JOIN

StkItem ON _bvSerialMasterFull.SNStockLink = StkItem.StockLink

WHERE (_bvSerialNumbersFull.SNTransType = 8) AND (_bvSerialMasterFull.CurrentLoc = 1) AND (StkItem.ItemGroup IN ('010', '020', '030', '040', '050', '060',

'070', '080', '100', '150', '300', '400'))

ORDER BY StkItem.ItemGroup, StkItem.Code, _bvSerialNumbersFull.SNTxDate