VB Code:
Private Sub CommandButton1_Click()
'Declare your data type - note that if you set a specific data
'type such as numeric, you must trap for non-numeric entries
Dim X As String
'Set variable equal to textbox value
X = TextBox1.Value
'Add data to cell A1 of Sheet2 - you can change this to any cell
'on any sheet witin the workbook
With ActiveWorkbook
Worksheets("Sheet2").Range("A1").FormulaR1C1 = X
End With
'Note that each time you click the command button, the data in cell
'A1 will be overwritten with the data in your text box
End Sub