Find And Update Row Values

I am writing a program that uses EXCEL forms to document all pending/back orders and saves the data to an EXCEL Sheet.When some items from a P.O have been fulfilled,I need to find the row where this order is located & replace it with the remaining quantity that needs to be delivered to the customers. EG.

Column A Column B Column C Column D
Status P.O. Description Quantity
------------------------------------------------------
Pending 1234 Table 10
Pending 2345 Chairs 20

Referring to the table above, when 8 chairs from P.O 2345 (order of 20 chairs) are being delivered to the customer, I need to find the row that contains this data & replace the quantity to 12 (User will input this value in a control form). I am using the MATCH function to find the row that contains the data but having problem in writing a code to replace the row values. Here is what I have written so far:

'to find the row that has an exact data match

i = Selection.FormulaArray = _

"=MATCH(RC[-4]&RC[-3]&RC[-2]&RC[1],ColumnD&ColumnG&ColumnE&ColumnH,0"

'replace the quantity to the remaining quantity(this is where the problem is)

lrow = ws.Rows("B" & (i + 6)).Select

'copy data to excel file

Cells(lrow, 5).Value = Me.txtPO.Value

Cells(lrow, 7).Value = Me.cboDescription.

Cells(lrow, 9).Value = Me.txtQuantity.Value