thank you
it solved only one problam... the rounding of the number.
I have two types of discounts one using * and the other using 
this solve the other problam but uses two lines.. is there another options ?
If Operation = "*" Then x = (UPrice * Discount)
If Operation = "" Then x = (UPrice  Discount)
Try this replacing your control names:

Dim vString As String

Dim vLen As Integer

Dim vNumber As Double

' get the length of the string

vLen = Len(Trim(Me.Text11))

' extract out the number

vString = Mid(Me.Text11, 2, vLen  1)

' convert the string to a double number with 2 decimal places

vNumber = CDbl(FormatNumber(vString, 2))

' display the result to a control on your form

Me.Result = Me.Price * vNumber
