Set cell value by macro not a formula

I want to set the value of a cell when running a macro, if the macro is not run the cell is blank and can be free format entry.

In the attached example I want to set the value of cell A1 on Sheet 1 when I run the macro. The value will be based on using the value in Cell F1 to lookup the the value in the table in sheet 2 column C where the value in Column A matches that value.

Hope that makes sense

Thanks