Depends, IS this Path going to be used in an Excel Worksheet Formula Or as a Variable in a VBA Procedure?
You have the right idea ( A1 + A2 + A3) but you have to add in all the " notations" required.
For example. Square brackets, quotes, dots, exclamation points, slashes, file extensions, etc
For VBA. A1 is File, A2 is Sheet name, and A3 is Cell Address
FullPath = $Path & "\" & Sheets(1).Range(a1) & ".xlsm" &
"!Sheets(" & Sheets(1).Range(a2) & ").Range(" & Sheets(1).Range(a3) & ")"
C:/Book1.xlsm!Sheets("Sheet1").Range("A1") YMMV