The quotepage Change value is computed as a difference in price from the Prev Close (Previous day's closing price) quotepage column. Some market data sources update this previous close value each time you log in, while others do not. Those that update it automatically should reliably show accurate Change, %Change, and Prev Close values.
If your data source does not supply this value, a custom column may be created to simulate the Change column. The Profession edition of Investor/RT is required to create a custom indicator to compute these values.
Right-click on any column heading and choose Add Custom Column. Then double-click on the New choice in the list. A new Custom Column Setup window will appear.
In the Type tab, select Custom Indicator; then click the New Cust. Ind. button. Create a custom indicator with the simple syntax SET(PREV, CL.1); CL - CL.1 and save this custom indicator with a name like "myChange". This custom indicator will serve two purposes. The first line will set the Prev Close quotepage value to the close of the previous daily bar. The second line will return a result of "Change" or current close minus previous days close. By setting the Prev Close here properly, the %Change, Change, and Prev Close columns should reflect this.
Now, back in the Custom Column Setup window, make sure the new "myChange" custom indicator is selected from the list. Also, make sure the periodicity control is set to Daily (the default).
Now, click the Add to Quotepage button. Provide a name for this custom column whem prompted, call it "Chg", for example. Now, the Chg column should appear in the quotepage. If the values still appear to be inaccurate, it's likely because the daily data is incomplete. The last two daily bars are required to be present in order for this to work properly. Download a few days of daily data on the quotepage (click Download Data button in main toolbar) to correct.
You may use the Rules tab of the Custom Column Setup window to customize the look of up/down prices, etc. (green for >0, red for <0, etc).