Based on picklist values i need to update Text field(Dynamically) in salesforce.

I have 2objects with Master-detail Relationship.

1st Object Paretn1,Paretn2,Paretn3,Paretn4,Paretn5 all are Number Fields.

I enter Partner2(Parent) some value

2nd Object

In child i selected in picklist(partner2) i am not get the "Cost/Hr$(NumberField)" here.

Picklist Values :-

When i select Partner1 with data when select on picklist for that Partner1 automatically need to display on "Cost(Number Field).

Like this Through Work flow i have done.

Rule Criteria:-  true

Field Update:-  

IF(ISPICKVAL(Resource_Role__c,"Partner1"), Opportunity_Margin_Template__r.Partner1__c, IF(ISPICKVAL(Resource_Role__c,"Partner2"), Opportunity_Margin_Template__r.Partner2__c, IF(ISPICKVAL(Resource_Role__c,"Partner3"), Opportunity_Margin_Template__r.Partner3__c, IF(ISPICKVAL(Resource_Role__c,"Partner4"), Opportunity_Margin_Template__r.Partner4__c, IF(ISPICKVAL(Resource_Role__c,"Partner5"), Opportunity_Margin_Template__r.Partner5__c,Null )))))

I have done single Workflow for these requirement.

CASE(Resource_Role__c,"PD(NA)", 207.7, 
"PD(UK)",174.95, "CN(NA)",149, "CN(UK)",157.4,"CN(Ind)",24.4, 
"CN(China",24.4, "CN(Japan)",120, "SS(NA)",134.95, "SS(UK)",128.95, "SS(Ind)",24.4,"EM(NA)",149,"EM(UK)",157.4,"EM(Ind)",24.4,"EM(Japan)",120,"Dev/QA(Ind)",24.4,"FTC Admin(Ind)",24.4, 
IF(ISPICKVAL(Resource_Role__c,"Partner1"), Opportunity_Margin_Template__r.Partner1__c, 
IF(ISPICKVAL(Resource_Role__c,"Partner2"), 
Opportunity_Margin_Template__r.Partner2__c, 
IF(ISPICKVAL(Resource_Role__c,"Partner3"), 
Opportunity_Margin_Template__r.Partner3__c, 
IF(ISPICKVAL(Resource_Role__c,"Partner4"), 
Opportunity_Margin_Template__r.Partner4__c, 
IF(ISPICKVAL(Resource_Role__c,"Partner5"), 
Opportunity_Margin_Template__r.Partner5__c,Null 
))))) 

)