How to make a conditional substitution in header?

[macdeport]

Here is my quote header in reply tab:

On %X:=sent%%dateformat(d/m/Y H:M:S)% %from(name,bracketMail())% wrote:<br>
> To: %to(name,bracketMail())%[[
> Cc: %cc(name,bracketMail())%]]
> Subject: %subject%
> Message-ID: %Message-ID%
[[> Reply-to: %reply-to(bracketMail())%
]]>

How to suppress > Reply-to: %reply-to(bracketMail())% if %reply-to(mail)% is identical to %to(mail)%?