You are trying to concantanate using the value that you are replacing in the
same cell.

2 options

1

use a different cell to concantanate the 2 values

Sub tst()

For Each cell In Columns(5)
cell.FormulaR1C1 = "=rc[-2] & rc[-1]"
Next

End Sub

or

assign the value that is in column d to a variable and concantante col c
with the variable

HTH

"caroline" wrote:

I am trying to concatenate 2 values (for instance new value in cell D4=
current value cell D4 + value Cell D3)

I get an error message 13 with this code:
For Each cell In Columns(4)
cell.Value = cell.Value & cell.Offset(0, -1).Value
Next

Any idea?
thanks
--
caroline