How to make validation with for loop inside if statement

Hello i this below code that deduct product quantity from the stock based on product quantity in grid view with id = gridagree
the issue is i want to deduct the products quantity with category =1 and put validation to check that all products quantity in gridagree if its bigger than the quantity in stock or not and if one product quantity bigger than the quantity in stoack the code should not executed
Category Id =gridagree.Rows[index].Cells[7].Text
Product Id = gridagree.Rows[index].Cells[3].Text)
Product Quantity in the grid =gridagree.Rows[index].Cells[5].Text

StoreClass s = new StoreClass(); if(//suggested code) { lblmsg.Text="Product quantity is bigger than current balance please change product qua ...