Calculating 99% in entire cell in Col M. Col M is filtered

[aligahk06]

Dear Expert,
I am in filtered mode and i want to calculate the 99% of Col M.
The filtered mode is like this M18,M20,M26,M46 and so on.
Is there any way that i can automatically calculate 99% of Filtered mode of ColM.

Please assist?
Rgds,
Aligahk06

[mdmackillop]

=SUBTOTAL(9,M:M)*0.99

[aligahk06]

Actually i have already value in column M Cell.Since the sheet is in filtered mode i want each value of the filtered cell in Col M to change 99% of the existing value.

Hope u undersatnd my query?

Rgds,
Aligahk06

[mdmackillop]

Sub My99()
Dim rng As Range, cel As Range
Set rng = Intersect(Columns(13), ActiveSheet.UsedRange).SpecialCells(xlCellTypeVisible)
For Each cel In rng
cel.Value = 0.99 * cel.Value
Next
End Sub

[aligahk06]

While executinf the program there is error like-
Run time error 91,
Object variable or with block variable not set.
Any help?

[mdmackillop]

While executinf the program there is error like-
Run time error 91,
Object variable or with block variable not set.
Any help?
Not really. Why not post a sample workbook includimg all your code?