[dba-VB] How to specify a relative path to an MS Access db in app.config?

Hi All --

That should be simple(?) but google somehow doesn't give any useful feedback
(or I'm missing it).

I wanted to have the following connection string from app.config to use
relative path to MS Access db - relative to the folder where app.config (its
assembly) will be installed on target system:

<connectionStrings>
     <add
name="ProductPicturesLocator.Properties.Settings.TestDataConnectionString"
        connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data
Source=.\Database\TestData.mdb"
        providerName="System.Data.OleDb" /> </connectionStrings>

If I write:

Data Source=.\Database\TestData.mdb

it works on start-up and when I work with main form, but as soon as I use,
e.g., OpenFile fialog, which changes default folder main form's update which
is bound do a dataset which uses the above connection string fails to update
db as it gets now improper fullpath  for db...

Isn't there something like 

Data Source=~\Database\TestData.mdb

or

Data Source={Application}\Database\TestData.mdb

or

...

way to specify "stable" relative path to the MS Access db - relative to the
app.config's assembly location?

I do not want to use DSN...

Thank you.

--
Shamil