How to multiply two value from two fields

[fdtoo]

I have the following fields in table A:

GL_ID|GL_Name_VC | Amount |Period_TI|Year_SI
===================================================
1000| Inventory| 8,000.00 | 01 | 2005
===================================================
1000| Inventory| -3,000.00 | 02 | 2005
===================================================
1000| Inventory| 5,000.00 | 02 | 2005
===================================================

the fields above have the following datatype:

Fields | Datatype
===================================
GL_ID | Integer
GL_Name_VC | Variable Character
Amount | Integer
Period_TI | TinyInteger
Year_SI | SmallInteger

The above database is running on Microsoft SQL Server 2000 and i would like to query
for a report that looks something as below:

GL_ID|GL_Name_VC |Period_01|Period_02 |Total_YTD
================================================
1000 | Inventory | 8,000 | 2,000 |10,000

Percentage| 10% | 20% | 0
================================================
Total | 800 | 400 | 1,200

The Total row is calculated by multiplying the percentage row by the Inventory amount in
each Period.

Guys, hope someone out there can help me with the sql command for the above report?