Sub test()
Dim i As Long
Dim c As Range
Dim offsetindex As Long
Dim delRng As Range

    Set c = ActiveSheet.UsedRange.Find("1234")

    While Not c Is Nothing
        
        Set delRng = c
        offsetindex = c.Column +  1 
        
        Do While Cells(c.Row, offsetindex).MergeCells = True
            Set delRng = Union(delRng, Cells(c.Row, offsetindex))
            offsetindex = offsetindex +  1 
        Loop
        
        delRng.EntireColumn.Delete
        Set c = ActiveSheet.UsedRange.FindNext
    Wend
    
End Sub