How to pass values to a system view form

[Donato_Speidel]

I have 3 tables: Service Calls, Customers & Sites.

In Service Calls table there are several columns two of which are [Customer ID] & [Site ID]. Both are references to the respective tables.

Sites has the column [Customer ID], it is also a reference to the customer table.

When entering a new record in to the Service Calls form I select a [Customer ID] from a drop-down. Next I can select a [Site ID] from a drop-down. The drop-down options for [Site ID] are filtered to only allow choices of sites that reference the selected customer.

All is good so far…

When I need to add a site that does not yet exist I choose “new” from the [Site ID] drop-down. This opens a form for a new row in the table Sites.

On this form the [Customer ID] field is blank and I need to select the [Customer ID] again. How can I pass the value of [Customer ID] from the current row of Service Calls to the new site form so it is not necessary to choose the customer again?