This example sets the x values for series one in Chart1 to the range B1:B5 on Sheet1.
Charts("Chart1").SeriesCollection(1).XValues = _
Worksheets("Sheet1").Range("B1:B5")
This example uses an array to set values for the individual points in series one in Chart1.
Charts("Chart1").SeriesCollection(1).XValues = _
Array(5.0, 6.3, 12.6, 28, 50)