Here is a snippet of code from my app where I did it. I hope it helps.
Dim success As Boolean
Const ChunkSize = 512000
Dim BlobData() As Byte
Dim DataLength As Long
Dim FileOffset As Long
record_set.Open "files_t", , adOpenStatic, adLockOptimistic, adCmdTable
'open image file
Open "filename" For Binary Access Read As #1
' add a new record to insert immage into
record_set.AddNew
DataLength = LOF(1)
' read and store image
FileOffset = 1
Do
If FileOffset + ChunkSize <= DataLength Then
ReDim BlobData(ChunkSize)
Else
ReDim BlobData(DataLength - FileOffset + 1)
End If
Get #1, FileOffset, BlobData()
record_set.Fields(columns(0)).AppendChunk BlobData()
FileOffset = FileOffset + ChunkSize
Loop While FileOffset < DataLength
Close #1