For item 2, there is the File System Object

http://msdn.microsoft.com/en-us/library/aa265304%28v=vs.60%29.aspx

Set fso = CreateObject("Scripting.FileSystemObject")

fileName = fso.GetFileName(fileName)

Set fso = Nothing

Here is the docs on item 1:

http://manual.pvxplus.com/directives/get_file_box.htm

So maybe something like:

oScript.Execute("InitialDir$ = ""S:\SERVER\PATH""")

oScript.Execute("GET_FILE_BOX READ FileName$,InitialDir$,""" & message & """")

looks like you can even define a file extension filter if you want.

[EDIT] This might be a little cleaner:

initialDir = "S:\SERVER\PATH"

oScript.Execute("GET_FILE_BOX READ FileName$,""" & initialDir & """,""" & message & """")

I been trying to do a similar thing.  I have tried the script above but keep getting the following error:

OLE Error Number: -2147467259

Description

Language: VB Script

Script line: 32

Script Column: 0

MS Script Link Error Information

User...  ERP100TEST Date...  7/16/2013 Time...  12:00:13

OLE Error Number...  -2147467259 Description........  Language...........  VBScript

Script Line........  32 Script Column......  0

1 : '   

2 : ' Sage 100 ERP system variables   

3 : '   

4 : MAS_SCR_CMP = "NKC"   

5 : MAS_SCR_USR = "bjc"   

6 : MAS_SCR_MOD = "A/P"   

7 : MAS_SCR_DTE = "20130716"   

8 : MAS_SCR_HWD = "E:\APPS\sage\Sage 100 Advanced ERP\MAS90\home"   

9 : MAS_SCR_LWD = "E:\APPS\sage\Sage 100 Advanced ERP\MAS90\soa"  

10 : MAS_SCR_LIB = "E:\APPS\sage\Sage 100 Advanced ERP\MAS90\AP\AP_VENDOR.M4L"  

11 : MAS_SCR_PNL = "PMAIN"  

12 : MAS_SCR_OBJ = "BT_LINK_1"  

13 : MAS_SCR_MSG = ""  

14 : MAS_SCR_PFM = ""  

15 : MAS_SCR_CS   = 1  

16 : MAS_SCR_DBG  = 0  

17 : MAS_SCR_ERR  = 0  

18 : '  

19 : ' form variables passed in by Customizer  

20 : '  

21 : AP_Vendor_bus_UDF_DRAWING = ""  

22 : '  

23 : ' language  : VBScript  

24 : ' file name : ..\cm\script\001.txt  

25 : ' script begin  

26 : '  

27 : Dim objShell  

28 : Dim strFileName  

29 : Dim strFilePath  

30 : Dim objFile  

31 : Set objShell = CreateObject("Shell.Application")  

32 : Set objFile = objShell.BrowseForFolder(0,"Choose a file:",&H4000,"S:\Part Control Docs\Current Parts")  

33 : strFileName = objFile.Title  

34 : strFilePath = objFile.self.Path  

35 : MsgBox "Just the file name: " & strFileName & vbcrlf & "The full path: " & strFilePath  

36 : Set objFileName = Nothing  

37 : Set objFilePath = Nothing  

38 : Set objShell = Nothing  

39 : retVal= oBusObj.SetValue("UDF_DRAWING$", strFileName)  

40 :  

41 : '  

42 : ' script end  

43 : '

BroseForFolder is really designed for just selecting folders, not files, which is why I suggested using the MAS 90 file dialogs above.

A brief google of the error comes up with others who have dealt with it already. www.tek-tips.com/viewthread.cfm