Replace 
===
REPLACE('12-345-67', '-', '')

Add leading zeros (left pad)
===
Right("000000" + Str([EmployeeID]),6)

Pretty print hard disk sizes
===
IF 
LEN(STR([Size])) > 9 THEN LEFT(STR([Size]), 1) + "." + MID(STR([Size]), 2, 1) + " TB"
ELSEIF LEN(STR([Size])) > 8 THEN LEFT(STR([Size]), 3) + "." + MID(STR([Size]), 2, 1) + " GB"
ELSEIF LEN(STR([Size])) > 7 THEN LEFT(STR([Size]), 2) + "." + MID(STR([Size]), 2, 1) + " GB"
ELSEIF LEN(STR([Size])) > 6 THEN LEFT(STR([Size]), 1) + "." + MID(STR([Size]), 2, 1) + " GB"
ELSEIF LEN(STR([Size])) > 5 THEN LEFT(STR([Size]), 3) + "." + MID(STR([Size]), 2, 1) + " MB"
ELSEIF LEN(STR([Size])) > 4 THEN LEFT(STR([Size]), 2) + "." + MID(STR([Size]), 2, 1) + " MB"
ELSEIF LEN(STR([Size])) > 3 THEN LEFT(STR([Size]), 1) + "." + MID(STR([Size]), 2, 1) + " MB"
END