populate drop down with horizontal range of merged cells

[spacely]

I have values in a horizontal range of merged cells that I need to appear in a combobox drop down (a form). So, a value in merged F1-R1, and a 2nd value in merged S1-AE1. I'd like to avoid VBA. But, if it's tough to add a 3rd entry in the same style, I suppose an initialization button would be OK.

Thanks for helping!

 

[spacely]

Actually, VBA is not good as initializer, because the book needs to remember the drop down settings last saved with the book. That would be lost when re-initializing. Some kind of transpose of horizontal to vertical, but for merged cells, is needed to just connect the drop down list to the data