Dynamic Combo Box: Form control vs active X

I've been asked to help with a combo box problem a co-worker is having. He has 2 combo boxes and he wants the options in the second one to be determined by the selection in the first. There is a list of 150 possible things he wants to show in the second but depending on what is selected in the first only 10-15 specific ones need to be in the second box at any one moment in time.

I am okay with VBA so if it was me I would use the ActiveX combo box and populate the second one on the fly using a bit of code. However my co-worker has no knowledge of VBA and was asking if I know of a way to do it using the "simpler" Form controls and building a dynamic list somehow. To be honest I don't know if this is possible...using a formula maybe?

If anyone knows how this could be done using the Form control combo box only then that would be great. :-)

Regards
Rob

You can do it with forms controls and VBA, unless you really need to, you're better off avoiding ActiveX controls on the worksheet. Depending on what filters the list (and assuming you don't need to type into the box - that a dropdown is fine) then it may be possible without code