计算结果错误

[dtsdts]

利用ado学习自定义函数
Public Function balance(s As Currency, z As Currency) As Currency
Dim y As Double
Dim strsql As String
Dim rs As New ADODB.Recordset
Dim cnn As New ADODB.Connection
Set cnn = CurrentProject.Connection
strsql = "select * from 表1 order by id"
rs.Open strsql, cnn, adOpenKeyset, adLockOptimistic
y = 0
Do While Not rs.EOF
s = rs("收入")
z = rs("支出")
balance = s - z + y
rs.MoveNext
y = balance
Loop
rs.Close
Set rs = Nothing
Set cnn = Nothing
End Function

将上面的函数用在查询1里计算余额，计算过程中没有提示任何错误，但结果是错误的
请教老师，主要错误在什么地方，以后写代码时应该注意些什么？
谢谢！

[liangyiqin]

你将s,z的值转换成double型后在计算一下，看看结果是否正确。

[OracleRoob]

balance   =   nz(s,0)   -   nz(z,0)   +   nz(y ,0)