I've been remapping my cursor keys like that since the '80s (remember SuperKey?).
(Except my "UP" key is Ctrl-i, maybe you meant i instead of u)
You can't do what you want in Macro Express. I couldn't live without Macro Express, but also need to have the cursor arrows repeat.
So I also use AutoHotkey, which is a very powerful free scripting program, but for me difficult to use except for simple stuff (like arrow key macros). There are also people out there who will write some very complicated code using AutoHotkey, often for free. So I do have a half dozen AutoHotkey utilities but the stuff I write for myself is usually using Macro Express.
The AutoHotkey script to do what you want is basically:
$^l::Send, {Right}
$^j::Send, {Left}
$^i::Send, {Up}
$^k::Send, {Down}
And this is why I no longer bug the Macro Express coders to include a "repeat" capability.
By the way, I also use a system level key remapper to put the Control key next to the "a" key, where it was always intended to be!