Hi Richard,
I am a beginner Access user and I am using 2007 version. I have an option group on my main form called OptionGrAgeCategory which has 2 choices: Neonatal and Adult. I have a combo box on a subform within this main form and it's called cboTypeofTherapy. I have 2 lookup tables that I'd like to populate the combo box with depending on user selection. So, for example, if the "Neonatal" option is chosen on the main form, then I would like to populate cboTypeofTherapy (on the subform) with data from the table NeonatalTherapy. If "Adult" is selected, then the combo box would be populated with data from the table AdultTherapy.

I am using If/Then/Else/End If to indicate RowSource changes of the combo box in the AfterUpdate of the Option group, but it's not recognizing the subform. I'm not sure how to correct this or if this is the right approach. Any help would be great.

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Answer from Richard Rost:

This tutorial should help you. It's not EXACTLY what you're looking for, but it will get you started. Instead of populating the data in a 2nd combo box, you're just going to apply the same technique to the data in a subform or second form.

I get asked this question all the time. You've got two or more combo boxes and you want the first one to filter the second one. I get asked this so much that I recorded a video tutorial explaining how to do it:

http://599cd.com/tips/access/two-combo-boxes?key=BlFAlEx