Hello Mariela:
During one of my GM-GTE implementation at a University i came across the same scenario where they had many huge grants and they had a requirement from Grantor to report budget and hence their commitments/actual at a very detailed level. GM-GTE is a solution to meet sponsor's reporting requirement without compromising company Chart of Accounts. GM-GTE has provided us a flexible dimension of Sponsored class and they can be opened based on sponsor's reporting lines. What we did was to derive Grant and keep commitment item as empty in FMDERIVE against source fields of GL + Internal order and had we had opened commitment item with category 50/3 for every such sponsored class and had mapped them in GMDERIVE. User while data entry against an expense say , had to enter GL and IO and give commitment item manually , they manual entry of commitment item derived desired sponsored class and this is the standard way to meet such requirement. I hope this helps.
Thanks