Can I extract specific text from the middle of a string?

This should work. Admittedly some brute force involved here, but the formula does have some repetitive elegance to  it at least.

var text SOne   = [Pickup Description];

var text STwo   = NotLeft($SOne,"S");

var text SThree = NotLeft($STwo,"S");

var text SFour   = NotLeft($SThree,"S");

var text SFive    = NotLeft($SFour,"S");

var text SSix     = NotLeft($SFive,"S");

var text SSeven= NotLeft($SSix,"S");

var text SEight   = NotLeft($SSeven,"S");

var text SNine= NotLeft($SEight,"S");

var text STen   = NotLeft($SNine,"S");



If(

Begins($SOne,"5"), "S" & Left($SOne,4),

Begins($STwo,"5"), "S" & Left($STwo,4),

Begins($SThree,"5"), "S" & Left($SThree,4),

Begins($SFour,"5"), "S" & Left($SFour,4),

Begins($SFive,"5"), "S" & Left($SFive,4),

Begins($SSix,"5"), "S" & Left($SSix,4),

Begins($SSeven,"5"), "S" & Left($SSeven,4),

Begins($SEight,"5"), "S" & Left($SEight,4),

Begins($SNine,"5"), "S" & Left($SNine,4),

Begins($STen,"5"), "S" & Left($STen,4))