HFM rule help

This is an HFM rule we have:

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HS.Clear "A#A:123100.C2#EndBal.C3#Equitization"

HS.Exp "A#A:123100.C2#EndBal.C3#Equitization = A#A:611000.C2#EndBal.C3#Equitization"

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Though #C1 is not defined above, What the rule is doing is copying every A:611000 #C1 data point to the like A:123100 #C1 data point

What I need to happen is for the rule to copy A:611000 #C1 (all members) to a A:123100 #C1 specific member.

For example:

I need source A:611000 with #C1 = SubAccount1 or SubAccount2 or SubAccount3 to go to A:123100 #C1 SubAccount1, leaving #C2 and #C3 as is.  Only A:123100 #C1 = SubAccount1 is valid for accounting purposes.  Corp Acctg does not want data at the target A:123100 #C1 SubAccount2 or #C1 SubAccount3.