I am sorry to be bothering you I am trying to say that if the vendor name and the
name on the list box match then the on hand quantity for that vendor in the inventory sheet should be displayed in the on hand quantity cell in the summary sheet

here is my pseudo code:
select inventory wksheet
Count the total number of rows in the inventory sheet
repeat from row#2 to the total number of rows calculated above
If the vendor name for the row(Cell H) is equal to the vendor name in the list box
total_quantity_on_hand=total_quantity_on_hand
+On_Hand_Quantity(Cell D)
End IF
Loop
Select Summary Worksheet
Write the total_quantity_on_hand value to the cell in Summary worksheet

Dim intQuantityOnHand As Integer
Dim intOnHandQuantity As Integer
'Go to inventory worksheet
Worksheets("Inventory").Select
'Count number of rows
'Select cell a1
Worksheets("Inventory").Range("a1").Select
'Select the current region that contains the cell a1
ActiveCell.CurrentRegion.Select
'Count the rows that you selected
intRowCount = Selection.Rows.Count
Worksheets("summary").Select
For i = 0 To 30
If Worksheets("Inventory").Range("H" & i).Value = strVendor _ (intQuantityOnHand) Then
intQuantityOnHand = intQuantityOnHand + intOnHandQuantity
strVendor(intQuantityOnHand) = Worksheets("Inventory").Range("d" & i).Value
End If
Next i
For i = 1 To intVendor
Worksheets("Summary").Select
Next i