VLOOKUP VBA to only target blank cells

[KGards7]

Hey all I have two workbooks:
1. "SAS MI Data"
2. "OIMDataRefresh_DMZ"

I want to set up a button to run 3 vlookups in the SAS MI Data workbook:

1. To be run in Column S in SAS MI Data workbook
If Column R in "SAS MI Data" matches column F in "OIMDataRefresh_DMZ" then show the contents of column F in column S BUT only for blank cells in column S (basically don't override any information already in column S)

2. To be run in column T in SAS MI Data workbook
If column R in "SAS MI Data" matches column H in "OIMDataRefresh_DMZ" then show the contents of column H in column T BUT only for blank cells in column T (basically don't override any information already in column T)

3. To be run in column U in SAS MI Data workbook
If column R in "SAS MI Data" matches column J in "OIMDataRefresh_DMZ" then show the contents of column J in column U BUT only for blank cells in column U (basically don't override any information already in column U)

Sorry if all that information is overkill, its essentially the same exact formula run 3 times for different columns for the VLOOKUP but its imperative that it only targets blank cells in columns S, T and U. Any help would be GREATLY appreciated.

Thank you so much