Предполагая
A B
========
1) 1 2
2) 3 4
Тогда это поместит данные в C1:
Dim Data As Range, cell As Variant, buffer As String
Set Data = Range("A1:B1", Range("A1:B1").End(xlDown))
For Each cell In Data
If (buffer = "") Then
buffer = cell.Value
Else
buffer = buffer & " " & cell.Value
End If
Next
Range("C1").Value = buffer