Function f1()

a1 = InputBox("Text", "Window")
a2 = InputBox("Text2", "Window2")

If IsNumeric(a1) = False Or IsNumeric(a2) = False Then
MsgBox ("ploho")
Call f1
End If

D1 = a1
If D1 < 0 Then
MsgBox ("Нет точек пересечения")
Call f2
ElseIf D1 > 0 Then
x2 = a1
y2 = a1
MsgBox ("(" & x2 & "; " & y2 & ")"), vbInformation, "Vivod"
End If
x1 = a1
y1 = a1

MsgBox ("(" & x1 & "; " & y1 & ")"), vbInformation, "Vivod"

MsgBox ("(" & x1 & "; " & y1 & ")" & "," & "(" & x2 & "; " & y2 & ")" & "," & "(" & x3 & "; " & y3 & ")" & "," & "(" & x4 & "; " & y4 & ")" & "," & "(" & x5 & "; " & y5 & ")" & "," & "(" & x6 & "; " & y6 & ")" & "," & "(" & x7 & "; " & y7 & ")" & "," & "(" & x8 & "; " & y8 & ")" & "," & "(" & x9 & ";" & y9 & ")" & "," & "(" & x10 & ";" & y10 & ")"), vbInformation, "Vivod konechnii"

End Function