grid question?

Hello, I have a wx grid that is placed below a row of buttons. there is one button per column. I would like a user to be able to select a grid cell, push the button above this cell’s column and have a menu appear where they can set the cells background color.

I am not sure how to make a menu appear when its not from within a menubar?

Also, how would I go about making the size of the buttons so that each button is aligned perfectly with its column?

on a related note I added this grid to a sizer. the grid area resizes but the columns and rows do not. Is it possible to make it so that the actual cells/row/columns are resized as well?

thanks for the help!

Jeff