Example of locating a cell and populating values from a combo box

UserForm

Private Sub btnSubmit_Click()
    
    Dim found As Boolean
    found = False
    Dim i As Integer
    ' Start at the second cell
    i = 2
    
    ' While Combo box value does not match the target cell's value or as long as the cell has a value
    Do
        ' Bump the cell index position
        i = i + 1
        MsgBox Cells(i, 1).Value & " = " & cbUnitNo.Value
        ' Set a marker to make sure we actually found a match
        ' "CStr" converts the value to a String.  I had to do this because
        ' I think Excel is automatically converting the cell or combo box
        ' value to a integer.
        If CStr(Cells(i, 1).Value) = CStr(cbUnitNo.Value) Then
            ' We've found the match, set to true
            found = True
        End If
    Loop Until CStr(Cells(i, 1).Value) = CStr(cbUnitNo.Value) Or Cells(i, 1).Value = ""
    
    ' If we've found the value in the Unit No. column
    If found Then
        ' Set the appropriate column values.  Notice I'm just using "i", my index in the loop
        ' as the row index.
        Cells(i, 2).Value = tbMeterReading.Value
        Cells(i, 3).Value = tbDate.Value
        ' Hide the form...or whatever you want.
        Me.Hide
    ' If you can't find a match (probably because someone mistyped a unit number)
    Else
       '  Pop a message box to tell them there was a problem.
       MsgBox "Could not find the Unit Number in the spreadsheet"
    End If
    
End Sub


' Dynamically initialize the combo box
Private Sub UserForm_Initialize()
    
    Dim i As Integer
    ' Start at the second cell
    i = 2

    ' Iterate over the cells in column A (e.g. "1") as long as the value is not empty
    Do While Cells(i, 1).Value <> ""
        '  Populate the cell value in the combo box
        cbUnitNo.AddItem Cells(i, 1).Value
        i = i + 1
    Loop
    
End Sub