Confused, please help

Hi,

I've designed a macro that will be used to keep track of stock levels. Thanks to Ivan i can now add to the levels of stock using the following code...

rivate Sub Check(Tbx As MSForms.TextBox, sht As Worksheet, Comb As MSForms.ComboBox)
Dim curpos As Double
Dim row As Double, col As Single

curpos = Tbx.SelStart

If Comb.Text = "" Then MsgBox "No Stock selected": Exit Sub
If Not ValidateNumeric(Tbx.Text) Then
Beep
Tbx.Text = Left(Tbx.Text, curpos - 1)
MsgBox "Please use numbers only!", vbExclamation, "Invald charatcer"
Else
row = FindPart_Row(sht, Comb.Text)
If row = 0 Then GoTo Err
If InStr(1, sht.Index, 1) > 0 Then
col = 5
Else
col = 4
End If
Sheets(sht.Name).Cells(row, col) = Tbx.Value
End If

Exit Sub
Err:
MsgBox "A critical error has occured...contact creator", vbCritical
End Sub

and

Function FindPart_Row(Sh As Worksheet, Str As String)
Dim topcell, bottomcell, searchRg As Range, x, Find As Range, y

With Sh
Set topcell = .Cells(3, 1)
Set bottomcell = .Cells(65536, 1)
End With

If IsEmpty(topcell) Then Set topcell = topcell.End(xlDown)
If IsEmpty(bottomcell) Then Set bottomcell = bottomcell.End(xlUp)

Set searchRg = Range(topcell, bottomcell)
x = searchRg.Address
y = Sh.Name
On Error Resume Next
Set Find = searchRg.Find(What:=Str, LookIn:= _
xlFormulas, LookAt:=xlWhole, SearchOrder:=xlByRows, SearchDirection:= _
xlNext, MatchCase:=True)
If Not Find Is Nothing Then
FindPart_Row = Find.row
Else
FindPart_Row = 0
End If
End Function

The problem is i don't understand it! I need to chnage the code slighlty so that i can remove stopck as well as add it. I don't know how this code tell assigns a textbox's contents to a cell. All i want to do is keep the same style but insert the textbox contents 1 cell to the left...

I'm very confused and running out of time (has to be finished in a few weeks!)

Any help would be appreciated. I'm using excel 97.

Thanks in advance , Matt