Byte Array to a Signed Integer in VB6

Unfortunately no built in function, you need to write one. Here is a quick sample to get you started.

Private Function BArrayToInt(ByRef bArray() As Byte) As Integer
    Dim iReturn As Integer
    Dim i As Integer

    For i = 0 To UBound(bArray) - LBound(bArray)
        iReturn = iReturn + bArray(i) * 2 ^ i
    Next i

    BArrayToInt = iReturn

End Function

CopyMemory

Air code (may crash your PC, cause dinosaur attack, etc).

Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (dest As Any, _ source As Any, ByVal bytes As Long)  

Dim a() As Byte 
Dim n As Integer 
 'get the bytes somehow into a()
CopyMemory n, a(0), 2 

I know this is OLD but people like me still find it useful to get me pointed in the right direction.

@jac solution did not work for me but I came up with a mod to his code that solved a limitation of it that would not convert the result which which was still inside the negative bounds of a LONG. That is hard to explain but here is the clumsy code that solves that limitation:

Function BArrayToSignedLong(ByRef bArray() As Byte) As Long
 'NOTE: bArray can now be UNSIGNED if your final result is in +/- 2^31 range of a LONG
 Dim twoTo32 As Currency 'just temporary to handle intermediate results outside of LONG limits
 Dim cReturn As Currency 'this is 64 bits than can handle going over 2^32
 Dim iReturn As Long  'this is signed 32 bit to send back
 Dim i As Integer
 twoTo32 = 2 ^ 32 'make this next up or down count loop direction based on the endian order you need
 For i = 0 To UBound(bArray) - LBound(bArray)
    cReturn = cReturn + (bArray(i) * (256 ^ i))
 Next i
 If cReturn > twoTo32 / 2 Then
     cReturn = cReturn - twoTo32
 End If
 iReturn = cReturn 'take Currency value back to a LONG variable
 BArrayToSignedLong = iReturn
End Function