regex to check 4 digit number code example

Example 1: regex numeric digits

' 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

Example 2: regex match any number of digits

For matching an integer number of one single char/digit, specify:
[0-9]
But for matching any number of more than one char/digit; add "+":
[0-9]+
Example for matching hour with minutes of HH:MM format in a file:
grep "[0-9]\+\:[0-9]\+" file.txt