How add the Field Relationship for ‘Request Type’ pick list field based on the value of ‘Phase’ short text field of a Type.

How add the Field Relationship for ‘Request Type’ pick list field based on the value of ‘TPhase’ short text field of a Type.

For example,

Initially Request Type has Build, Deploy and Build & Deploy values

1) If TPhase value is "Ready to Build" then the 'Request type' should have Build option only

2) If TPhase Value is not "Ready to Build" then the 'Request type' should have both Deploy and Build & Deploy not Build.

I could not see TPhase in Source Field list of the field relationship column. We use Integrity Server 2009.

Is there any other possible way to restrict Request Type values.

Thanks in advance.