Connect to network share from Win CE 5.0 using vb .net 2.0

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.NET2.0

VB

Windows

.NETCF

.NET

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Hope someone can help me because i don't know what to do anymore.
We have a little Box running Windows CE 5. Only connections are 2x LAN and 4 Serial -Ports. No screen, no Keyboard.
I need to connect to a network share which contains a file. The content of the file has to be read (no problem with this). To get to the file, i have to supply Network Credentials.
And here is where i'm stuck. I don't know how to provide these.
A simple file copy seems to work, but you have to provide credential. But with no screen, who can check if the dialog popped up. So i need a way to connect to the network share (using .Net Compact Framework 2.0).
I tried WNetAddConnection2 in a normal .net-project, without success(i'm wondering if the appropriate dll is present on this thing). As far as i remember i got the error-code 478.
Also tried the project "Connect to a UNC Path with Credentials" from here but with no luck(already connected and the function doesn't seem to like it).
Any suggestions in the right direction would be appreciated.