Only unique values to a combobox from multiple columns, vba

[einheri]

Is there a way to collect unique values from several columns (eg E4 to H1500) and put those values into a userform Combobox with no duplicates.

like: E4 F4 G4 H4
row1 Byan PDIV RSI2

Row2 E5 F5 G5 H5
RSI Byan T8 RS

and so on ......

Hope you understand
Thanks
Einheri

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[Khanzaki]

@Akuini ;
Above code serves the purpose and is more flexible ! Thankyou so much !!
Also I was thinking of a way to combine all the unique values from all the columns D ; E; H;L into one combobox Can this be achieved ?
To put it in a more specific way ; I have data in
Column O , U, AA, AG so on upto Column CO ie Step of 6 Total 14 Columns
I would like to have a unique list of all 14 columns
in 1 single combobox name prd15