VBA To Autofill Formula Over Column Data Calculate And Replace Original Data

Id like to apply a formula, any formula to an entire column if it contains data, and incorporate the original data in the calculation and then replace the original data with the result. I don't want to have to create new columns.

I'm using this to fix up database results; a common problem is dates in dot format e.g. 14.11.2008

All I have so far is an autofill formula that overwrites everything. Can someone help me with the rest? I'm using the SUBSTITUTE function to replace the dots '.' with slashes '/'

Sub Create_formula_result()

Dim Limit As Long
Dim r As range
Set r = range("A1")

r.FormulaR1C1 = _
"=IF(RC[0]"""",(SUBSTITUTE(RC[0],""."",""/"")+0) ,"""")"
Limit = ActiveSheet.UsedRange.Rows.Count
r.AutoFill Destination:=range(r, Cells(Limit, r.Column))

End Sub