All Gruner Corporation employees will be invited to the holi

1. All Gruner Corporation employees will be invited to the holiday (celebration) scheduled for next Friday .
holiday celebration = 节日庆祝活动
英语常用名词来做形容词
这里 holiday 是形容词, “节日的”
其他名词作形容的用法包括
coffee shop
music store
customer complaint
telephone message
computer program
等等
2. effective 可接介词 in 和 for
effective in sth 是固定用法
in 是这个短语的固定介词
effective in attracting customers
的意思是
对吸引顾客有效力.
举个类似例句：
Keeping calm can often be effective in diffusing tense confrontations