API VB Troubles BSP_GetFilename

[smorrowatwork]

:?
I've had very good luck with the API from VB so far, but am stumped on using the BSP_GetFilename API Call. Below is my VB code with a description of the setup and results. Any assistance is solving this conundrum would be appreciated.

Setup:
Bsplayer Ver 0.86 Build 501 16 Sep 2003
Running and playing .avi file named "BetterOffDead.avi"

VB Code:

Dim cds As COPYDATASTRUCT
Dim sbuf As String

bsp_hand = FindWindow("BSPlayer", vbNullString)

'Get filename
sbuf = String$(MAX_PATH, vbNullChar)
cds.dwData = BSP_GetFileName
cds.lpData = VarPtr(sbuf)
cds.cbData = 4
SendMessage bsp_hand, WM_COPYDATA, Me.hwnd, cds

Output:

sbuf = "????????????????" with the remainder of the buffer filled with the null character.

This tells me that the message to BSPlayer is being recieved, and the buffer is being modified, but the result back is all '?' and not the name of the file. By the way there is 1 too few '?' for 'BetterOffDead.avi'. I was thinking there might be Unicode vs ASCII characters issue.

I'm stumped.

-Steven