Failed to copy Field with expresion which contains call to function in Tablix SSRS

Question

In a SSRS report (VS 2019), in a Tablix I have a cell which contains an expression like below:

=Code.Quotient(Fields!MyField1.Value, Fields!MyField2.Value, -1)

where Quotient is a function I wrote in code.

When I do a copy of the Tablix (in the same report), for the copied Tablix, in the same cell, I have

=Code.Quotient

Is any way to copy correctly the Tablix?

The function is:

Function Quotient(ByVal numerator As Decimal, denominator As Decimal, custom as Decimal) As Decimal
    If denominator = 0 Then
        Return 0
    Else
        Return ((numerator / denominator) + custom)
    End If
End Function