title: Update field in subform based on field in modal dialog
body: <p>I have a master form (frmServices) with two sub forms (frmExpensesSubForm and frmMileageSubForm). Services and expenses are linked one to many with a serviceID field. frmExpensesSubForm  is a data sheet view containing expenseDate, Amount and a combo box for expenseType. If the expenseType chosen is "Auto Mileage" the frmMileageSubForm displays as a modal dialog with a reimburseRate specific to the expenseDate for the record in the frmExpensesSubForm. On the frmMileageSubForm when a distanceTravelled entry is made, the reimburseAmount is calculated as the product of the rate and the distance. All this is currently working.</p>
  
  <p>How, in VBA, do I update the Amount field in the frmExpensesSubForm to the calculated reimburseAmount when the "OK" button is clicked? I tried:</p>
  
  <pre><code>Private Sub Command1_Click()
      Forms!frmServices!frmExpensesSubForm.Amount = Forms!frmServices!MileageSubForm.reimburseAmount
  End Sub
  </code></pre>
  
  <p>but I get a runtime 438 error.</p>