Arrange raw data

Hi

How can I fix this problem:

The "raw" excel sheet looks like this:

A1:x
A2:x
A3:y
A4:z
A5:z
A6:z

B1:a
B2:b
B3:c
B4:d
B5:e
B6:f

And it have to look like this:

A1:x
B2:a[new line]b

A2:y
B2:c

A3:z
B3:d[new line]e[new line]f

The numbers of cells who have to be “melted” together will vary widely.

Hm, I tryed this macro:

Sub Makro2()
Dim Data As Variant,RW as long
RW = Range("B65536").End(xlUp).Row
Data = Range("A1:I" & RW)
x = 0
y = ActiveCell.Column
For I = 2 To UBound(Data)

If Data(I, 2) = Data(I - 1, 2) Then
If x = 0 Then x = I - 1
Data(x, y) = Data(x, y) & vbLf & Data(I, y)
Data(I, y) = Empty
Else
x = 0
End If
Next
Range("A1:I" & RW) = Data
Range(Cells(1, y), Cells(RW, y)).SpecialCells(xlCellTypeBlanks).EntireRow.Delete
End Sub

But it come with this error after a random number of cells, it is the same place the error comes when I run the macro without changing the sheet. What can it be?

The only infomation I have on the error is this:

Run-time error '1004': Application-defined or object-defined error.

And it mark this with yellow in the macro:

Range("A1:I" & RW) = Data