Merge Data Macro

I have been using the following code to fill data down a col. For example if a1=blue and a5=green and a7=red. The macro will fill a1(blue) down to a4, then take a5(green) to a6, then a7(red) etc.

Sub Filldown()
If ActiveCell.Text = "" Then
MsgBox "please start with a non-empty cell"
Exit Sub
End If
For Each x In Selection.Cells
If x.Text = "" Then
x.Value = x.Offset(-1, 0).Value
End If
Next x
End Sub

code works great, but I was hoping it could be changed so that instead of filling the data down it would merge the data down. So, in the example, a1:a4 would be merged leaving the word blue, a5:a6 merged, and a7:etc would be merged.
Is this possible?