Open the sample.xlsx file by macro
Workbooks.Open "Full_Name"
put that formula in C2 and drag it
Drag it? Where? Probably to the last nonblank cell in column B. Then find the row number of the last nonblank cell in column B using the End(xlDown).Row property (maybe use End (xlUp)) and assign this value to a variable, e.g. lRow. Look for such constructions in the forum. It's a lot.
Then create a reference to the range "C2:C" & lRow by assigning it to a variable, e.g. rngScope, and insert your formula into this range. It would be safest if the formula was in the R1C1 convention. More or less this way
rngScope.FormulaR1C1 = "=My_Formula_R1C1"
At this point, you have formulas in column C.
change the result in column C as paste as values
rngScope.Value = rngScope.Value
and save and close the file
ActiveWorkbook.Close True
And it's ready. 
If you have a problem with something, ask us.
Artik