Like I said, the function event works like this: you name a function which returns TRUE when the archiving should start.
The following came from the help:

Start/Stop Events

Events start and end process value archiving. Conditions which trigger an event may be linked to a tag or to scripts (C, VBS). In WinCC, events are differentiated as follows:

Binary Event: Reacts to changes in a Boolean process tag. For example, turning on a motor may start archiving of a process value.

Limit Value Event: Reacts to exceeding, falling short or reaching a limit value. Limit value changes may be in absolute or scaled numbers. For example, temperature fluctuations of more than 2% may trigger archiving.

Time-controlled Event: Reacts to a fixed point in time period or passage of a time period after process value archiving has started. For example, a log is issued after each shift change.

Function to Start Archiving

int Function Name ( );

Description

The function must return the value "0" (corresponds to FALSE) or "1" (corresponds to TRUE). Other values are not permissible. An archiving is triggered depending on archiving method and return value of the function.

For cyclic archiving, archiving is always triggered if the return value of the function is "1".

For acyclic archiving, archiving is always triggered if the return value has changed from the last function call. The first function call must return the value "1".

The function may be assigned on the "Events" tab control of the "Process tag properties" dialog.

Soyou'd need to create a function which would, as I said, return the result of tag1 * tag2. This function would be the event to trigger your archiving starts. That is assuming that for all the 44 situations you have the same tag1 and tag2. However if your event function has to be different for each of the 44 archive tags (tags 1 and 2 aren't always the same ones) I don't know how to help more...