Got it!!
Dim newCost As Double
newCost = Me.OperatingCost.Value
Dim myFrm As String
myFrm = "frmMyOpenForm"
DoCmd.Close acForm, myFrm
DoCmd.MyOpenForm myFrm, acDesign, , , acFormPropertySettings, acHidden
Forms!OpenForm.DefaultValue = newCost
DoCmd.Close acForm...