[AccessD] Format dollar amount inside messagebox

I have this code:

If Me.txtOldAmt <> Me.txtIncentiveAmt Then 'Split & Amt Changed
                            strMsg = "Are you sure you want to change
this incentive?" & vbCrLf & _
                                     "Amount will change from " &
Me.txtOldAmt & " to " & Me.txtIncentiveAmt

It displays as: "Amount will change from 2 to 4.5"

I would like it to show as "Amount will change from $2.00 to $4.50"

Any idea?