When NON Intercompany natural accounts are used in Segment4 then the segment 7

When NON Intercompany natural accounts are used in Segment4 then the segment 7 Intercompany segment should have a default value '0000'

We have Intercompany accounts and where we intercompany segment to populate when we do the intercompany transactions.
When general transactions are getting entered, in some places users are entering the intercompany segment even though not needed and HFM integration is erroring out.

approximately 2000 segment4 natural accounts are there
Out of which 100 are Intercompany accounts
Rest of them are normal segment4 natural accounts.

So here we have a requirement as below

When NON Intercompany natural accounts are used in Segment4 then the segment 7 Intercompany segment should have a default value '0000'