error in create formul1

[arumugavel(Legacy Member)]

Dear all,

i have create one formula for sum(amount)

i create one group by Group name filed for the sum amount with party name. but i trying to save error is occured "the remaining text does not appear in the formula"

the formula is

sum(GroupName ({Collection_Pending_sales_Report;1.PARTY_NAME})),(sum({Collection_Pending_sales_Report;1.ACT_PENDING_AMT}) / count({Collection_Pending_sales_Report;1.PARTY_NAME}))

please give solution for this.