Вот другой способ с for / next l oop
textbox1.text ="tradeIdno 268181090713],buyToken tradeIdno 748832411131],buyToken tradeIdno 81724814287],buyToken tradeIdno 4871814],buyToken"
Dim s As String = TextBox1.Text
Dim result as string = ""
dim atnumeric as boolean = false
for x as integer = 0 to s.length - 1
if isnumeric(string.substr(s,x,1))
atnumeric = true
result += string.substr(s, x, 1)
else
if atnumeric = true then
result += vbcrlf
atnumeric = false
end if
next
msgbox(result)