Private Sub Command1_Click()
Dim q As Double
Dim k As Double
Dim λ As Double
Dim date_q(10000) As Double
Dim b As Double
Dim i As Double
q = Text1
k = Text2
For i = 0 To 10000
    λ = i / 10000
    b = ((k + 1) / 2) ^ (1 / (k - 1)) * λ * (1 - (k - 1) / (k + 1) * λ * λ) ^ (1 / (k - 1))
    date_q(i) = b
Next i
For i = 0 To 10000
     If q > date_q(i) Then Next i
     If q = date_q(i) Then Exit For
     If q < date_q(i) Then Exit For
λ = (i - (date_q(i) - q) / (date_q(i) - date_q(i - 1))) / 10000
Text3.Text = λ
End Sub

for next是唯一对应的语句对，不能单独作为条件语句执行，你的If q > date_q(i) Then Next i是不符合语法规范的，应改为
For i = 0 To 10000
'这一句去掉，既然小于或等于都跳出循环，那么进入循环的必然是大于     If q > date_q(i) Then Next i
'这一句也可去掉，因为VB有<=的关系符     If q = date_q(i) Then Exit For
     If q <= date_q(i) Then Exit For
next

图解～Win7的装这软件显示不正常～将就点吧～