replacement with macro stop values from working in formula

hey everyone,

just a small note, im using a bit of an outdated excel version, excel 2003 to be exact.

for a small assignment i have been tinkering with the excel macro function.
the assignment involves importing different text files into 1 excel sheet and formatting them so they can be used in formula's and graphs.

the files that are delivered however use a . instead of a , as decimal seperator. this is where my problem starts.
ive gotten far enough to get everything working with the macro.
but when i use the replace function with CTRL+H to replace all the . for , everything is fine and the values all work in their formula's.

but as soon as i let me macro function replace these . for , the values all stop working.
as soon as i double click on the cell and proceed to click out of the cell, note: not changing anything, the cell works in my formula again.

the bit of code is use to replace the . with , is as follows:

Range("A2:K2").Select
    Range(Selection, Selection.End(xlDown)).Select
    Selection.replace What:=".", Replacement:=",", LookAt:=xlPart, _
        SearchOrder:=xlByRows, MatchCase:=False, SearchFormat:=False, _
        ReplaceFormat:=False

the macro im writing is going to be used by other people, so i'd love to find out what causes this problem so that i can automate the process as much as possible.

if anyone knows a solution, i'd very much appreciate the help.
thanks in advance,
Diederik

edit:
i just figured that a possible solution might be to prompt the same window CTRL+H opens using VB.
if anyone knows the code for this, please let me know. ive been fairly new to VB and mostly figuring things out by recording and looking at what kind of code that generates