regular expression for full file path with file upload

I have a regualar expression for file upload which verify that user must give the .zip files
Now my problem is that user can write a file name like
abc.zip  [instead of full path like c:/abc.zip or \\mysharedfoler\\abc.zip]

Which stuck some of my work



<asp:RegularExpressionValidator ID="rgvPreferredPicture" runat="server" ControlToValidate="flUpdJob"
            ErrorMessage="Invalid file type." ValidationExpression="^.+\.((ZIP)|(ZIp)|(ZiP)|(zIp)|(ziP)|(zip))$"
            Display="None" SetFocusOnError="true" />
...