Using Combo Box To Run Macro

I am trying to set up a combo box in my workbook so that when the item is selected from the list a particular macro will run according to the selection. I tried with the following codes but wonder why it is not executing when running the macro.

Option Explicit
Sub COUNTRYCURR2()
Dim shtInv As Worksheet
Dim shtT_Country As Worksheet
Dim Row As Long
Dim Row2 As Long
Dim lngEndRowInv As Long
Dim lngT_Country As Long
Set shtInv = Sheets("Inventory")
Set shtT_Country = Sheets("T_Country")
lngEndRowInv = shtInv. Range("A" & Rows.Count).End(xlUp).Row
lngT_Country = shtT_Country.Range("A" & Rows.Count).End(xlUp).Row
shtInv.Cells(1, 19).Value = "Country Code"
shtInv.Cells(1, 20).Value = "Currency Code".................