Converting asp to aspx encoding problem

[Satya]

Hi I am new using a group and using asp net and vb net.
I have the following problem.

To resume, in my aspx.vb page I have:

strListeGroup.Append("<input type='button' class='buttonPurchasing'
name='btnModify' value='Modify'
onclick=""document.location.href='USER_ADMIN_GROUP_MODIFY.ASPX?MODE=MODIFY&GROUP="
& strGroup & "&COMPANY=" & strCompany & "';"" tabindex='-1'>")

my problem is when strGroup = "Sophie's" then the aspx page doesn't
work.
In my aspx I got :
<input type='button' class='buttonPurchasing' name='btnModify'
value='Modify'
onclick="document.location.href='USER_ADMIN_GROUP_MODIFY.ASPX?MODE=MODIFY&GROUP=Sophie's&COMPANY=MyCompany'";
tabindex='-1'>
the problem seems to be in
onclick="document.location.href='USER_ADMIN_GROUP_MODIFY.ASPX?MODE=MODIFY&GROUP=Sophie's&COMPANY=MyCompany'
because of the " ' "

In my aspx page I have:
<%=strListeGroup.toString()%>

I try a lot of things but anythings work (
my encoding is utf-8

Please HELP me ! thank you !