In each of the 4 subprojects, add a custom Start field, say Start1 and in each subproject, enter the formula

= baselineX start, where X is the last saved baseline number for that project.

E.g. If Project A last saved baseline is Baseline7, the formula for for Start1 custom field in Project A will be = Baseline7 Start

If Project B last saved baseline is Baseline2, the formula for Start1 custom field in Project B will = Baseline2 Start

Now, in the Master Project, add a Start1 column and it will display the latest saved baseline dates for each subproject in this single Start1 column.

All you need to do is remember to update the formula for each subproject anytime, you save a new baseline.

Give us a shout if you need further help with this.

==
Planners' Place