Merging & multiplying cells

Hello,

I want to merge some cells using a criteria. To be more specific, let's speak on the file attached.

Beginning with the P5 cell I want to merge to the right groups of 4 cells for each name from the column J. Therefore the first group of merged cells will be P5:S5, the next group will be T5:W5 and so on until reaches 11 groups of 4 cells. The last group will be BD5:BG5.

I tryied a script like this but it says that there is a syntax error on the "Else" instruction: Range(Range("AB5").End(xlToRight).Offset(0, 1), Range("AB5").End(xlToRight).Offset(0, nrCat)).Select

    Dim i As Long
    nrCat = Range("O2").Value
    For i = 1 To nrCat
    If Range("AB5") = "" Then
    Range("AB5", Range("AB5").Offset(0, nrCat - 1)).Select
    Range("AB5") = "A"
    Selection.Merge
    Else
    Range(Range("AB5").End(xlToRight).Offset(0, 1), Range("AB5").End(xlToRight).Offset(0, nrCat)).Select
    Selection.Merge
    End If
    Next iCan you help me?

Thanks!