#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?sm)(?:^\[0\d{2}]|\G(?!\A)).*?\R\[\K\?{3}(?=.*?\R\[0)"
Local $sString = "[000] Foo" & @CRLF & _
"[???] Foo" & @CRLF & _
"[020] Foo" & @CRLF & _
"[???] Foo" & @CRLF & _
"[045] Foo" & @CRLF & _
"[???] Foo" & @CRLF & _
"[???] Foo" & @CRLF & _
"[100] Foo" & @CRLF & _
"[???] Foo" & @CRLF & _
"[???] Foo" & @CRLF & _
"[115] Foo" & @CRLF & _
"[???] Foo"
Local $sSubst = "1??"
Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst)
MsgBox($MB_SYSTEMMODAL, "Result", $sResult)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm