' Needs reference "Microsoft VBScript Regular Expressions 5.5"
Dim rRegex As Object
Set rRegex = CreateObject("VBScript.RegExp")

rRegex.Pattern = "[0-9]{8,9}"   ' 8 or 9 numbers
MsgBox rRegex.test("12345678")  ' True

rRegex.Pattern = "[0-9]+"       ' Numeric of any size
MsgBox rRegex.test("12345")     ' True