如何用VB实现在已经有文字的WORD的最后插入文字

Function bytetobin(m As Byte) As String '讲字节型数据转换成八位二进制字符串
Dim c$
c$ = ""
Do While m <> 0
r = m Mod 2
m = m \ 2
c$ = r & c$
Loop
c$ = Right("00000000" & c$, 8)
bytetobin = c$
End Function
'---------------------------------------------------------------------
Function reverse(m As String) As String '将八位二进制字符串颠倒顺序
Dim i%, x$
x = ""
For i = 1 To 8
x = Mid(m, i, 1) & x
Next i
reverse = x
End Function

Function Bintobyte(m As String) As Byte '将二进制串换成十进制
Dim x As String * 1, y%, z%
z = 0
For i = 1 To 8
x = Mid(m, i, 1)
y = x * 2 ^ (8 - i)
z = z + y
Next i
Bintobyte = z
End Function
'-------------------------------------
Private Sub command2_click()
Dim x As Byte, i%, fname$
fname = app.path & "\123.txt"
If Dir(