How calculate value based on form data and table data

[SteveL]

I have a form field which has a value of say, 50 (numeric
value). I also have a table (tblLaborRates) which has a
few records. One of the records is ID 6550. In that
record is a field named "Rate" which contains a value
0f .09 (again numeric).

What is the code I'd write which would calculate the
field value (50) times the correct record "Rate" of .09
IF a separate checkbox named "chkbxRate" has a value of
true, in otherwords, is checked?

In other words, if the checkbox is checked, go out and
find the correct record in the table, and multiple the
value in a particular field within that record by the
form field value of 50. (Answer should be 4.5)

Any help with this one much appreciated!

 

[Allen Browne]

Try a text box with Control Source of:
=IIf([chkbxRate] = True, DLookup("Rate", "tblLaborRates", "ID=6550") * 50,
Null)

More info on how to supply the arguments for DLookup():
http://allenbrowne.com/casu-07.html