Here's one that takes its input from, and writes the results to, the Windows clipboard. It will process multiple lines independently, and will transform this:

49.99*1.175
(49.99*1.175)*5

into this:

49.99*1.175 =	58.73825
(49.99*1.175)*5 =	293.69125

If you change the lines, copy them, and recalculate, then it will ignore anything after the = signs.