What version of Excel?
For 2003, from the [View] Excel menu, choose [Toolbars] then go with either
Control Toobox or the Forms tools. I generally prefer the Forms tools, but
each has a command button available and each has advantages/disadvantages.
If those aren't the type of buttons you want, you can also place shapes on a
worksheet and format their size, shape and color and add text to them and
then assign a Macro to run when they are clicked.