"Link" cell data if invoice numbers match

[Briar]

Hey folks,
We want to "link" cell info from one spreadsheet to the
next, if the corresponding invoice numbers match for an
order. For example, if cell A1 (invoice #) on one page
matches the value in B12 (invoice #) on another page, then
enter the value from cell C2 (from first page, it's a
dollar amount) in this cell. Can anyone help?
Thanks,
Briar