=IF($B6=7,VLOOKUP($F$5,'\\Server name & file bath\[File name.xlsx]July-Data'!$A$9:$R$7915,3,FALSE),

IF($C6=8,VLOOKUP($F$5,'\\Server name & file bath\[File name.xlsx]Aug-Data '!$A$9:$R$7915,5,FALSE),

IF($C6=9,VLOOKUP($F$5,'\\ Server name & file bath\[File name.xlsx]Sep-Data'!$A$9:$R$7915,7,FALSE), "Data is not Available yet")
) )

The server file contains 8 tabs; from May until Dec where each month data is in a separate tab.

So, if the user entered July in $B6 in the user file, the Vlookup will search in July tab of the server file.

I do not have any formulas in the server file. Thank you.