Определить среднее арифметическое положительных элементов матрицы

Dim a(2,2)
sum=0
k=0
for i = 0 to 2
    for j = 0 to 2
        a(i,j)=Int(rnd()*20-10)
        if a(i,j) > 0 then sum = sum+a(i,j): k=k+1
    next
next
msgbox iif(k>0, sum/k, "нет положительных элементов")

Function Matr(x1 As Single, x2 As Single) As Single
Sum = 0
k = 0
For i = 0 To x1
    For j = 0 To x2
        A(i, j) = Int(Rnd() * 20 - 10)
        If A(i, j) > 0 Then Sum = Sum + A(i, j): k = k + 1
    Next
Next
MsgBox IIf(k > 0, Sum / k, "нет положительных элементов")
End Function
 
Sub proga()
Dim A() As Single, m As Integer, n As Integer
n = InputBox("Введите кол-во строк")
m = InputBox("Введите кол-во столбцов")
ReDim A(n, m)
Matr n, m
End Sub

Option Explicit
 
Sub Matr(A() As Integer) 'Функция должна что-то возвращать (хотя и не обязана). Пусть будет Sub ...
Dim sum  As Long
Dim k As Integer
Dim i As Integer
Dim j As Integer
For i = LBound(A, 1) To UBound(A, 1)
    For j = LBound(A, 2) To UBound(A, 2)
        A(i, j) = Int(Rnd() * 20 - 10)
        If A(i, j) > 0 Then sum = sum + A(i, j): k = k + 1
    Next
Next
MsgBox IIf(k > 0, sum / k, "нет положительных элементов")
End Sub
 
Sub proga()
Dim A() As Integer, m As Integer, n As Integer
n = InputBox("Введите кол-во строк")
m = InputBox("Введите кол-во столбцов")
ReDim A(1 To n, 1 To m)
Matr A
End Sub