VBA combo boxes (ignore blanks + avoid duplicates)

Hello,

I have roughly 50 comboboxes in sheet "TR-Metric Pg2" that pull information off of another sheet called "CTC-Form." I would like to know if there is a way to ignore blank cells so that they do not show up in the combobox drop down menus. Also, is it possible to wirte VBA code so that you cannot pick the same data twice between all 50 comboboxes? Any help would be appreciated.

Thanks,

Pablo