This should do what you want based on your description. It assumes that
your values are in columns A and B on the active sheet, and the total
is then written to cell C1.

GetTotal() prompts for the distance and passes it to the function
TotalShorter(), which returns the total. You could make it more
flexible by assigning range names ("X" and "Y"), or by adding prompting
for the ranges (either addresses or rows and columns).

Option Explicit

Sub GetTotal()
Dim d As Single
Do
d = Application.InputBox(Prompt:="Enter a value between 0 and 10:",
Type:=1)
Loop While d < 0 Or d 10
If d = False Then
Exit Sub
Else
Cells(1, 3).Value = TotalShorter(d)
End If
End Sub

Function TotalShorter(distance As Single) As Integer
Dim X As Variant, Y As Variant
Dim z As Single
Dim i As Integer, total As Integer

' read the x and y ranges into the variants
X = Range(Cells(2, 1), Cells(11, 1))
Y = Range(Cells(2, 2), Cells(11, 2))

For i = 1 To UBound(X)
z = (X(i, 1) ^ 2 + Y(i, 1) ^ 2) ^ 0.5
If z <= distance Then
total = total + 1
End If
Next i
TotalShorter = total
End Function

Gary