Have textbox.value populate cells in a certain row and column

[Templemind]

I have a formula that doesn't quite seem to work. First I tried to make a formula to match the text in row 4 and then input the text from another box in a row below that. Does it matter if it is merged?

here is the code so far:

Private Sub SubmitButton_Click()
Dim emptyRow As Long
Dim emptyCol As Long
Dim Res As Variant
    With Sheet2
        Res = Application.Match(Roomnum.Value, .Rows(4), 0)
            If Not IsError(Res) Then
                emptyRow = .Cells(Rows.Count, 1).End(xlUp).Row + 1
            Else
                emptyRow = .Cells(Rows.Count, 1).End(xlUp).Row + 1
                .Range("C" & emptyRow).Value = Credittxt.Value
            End If
    End With
End Sub