Try this
Public Sub ProcessData()
Dim cell As Range
Dim MergedCell As Range
Dim NumRows As Long
Dim NumCols As Long
With Application
.ScreenUpdating = False
.Calculation = xlCalculationManual
End With
With ActiveSheet
For Each cell In Range("A1").Resize( _
.Cells.SpecialCells(xlCellTypeLastCell).Row, _
.Cells.SpecialCells(xlCellTypeLastCell).Column)
If cell.MergeCells Then
NumRows = cell.MergeArea.Rows.Count
NumCols = cell.MergeArea.Columns.Count
cell.UnMerge
If NumRows > 1 Then cell.AutoFill cell.Resize(NumRows), xlFillCopy
If NumCols > 1 Then cell.Resize(NumRows).AutoFill cell.Resize(NumRows, NumCols), xlFillCopy
End If
Next cell
End With
With Application
.Calculation = xlCalculationAutomatic
.ScreenUpdating = True
End With
End Sub